To answer this question correctly requires considering your values & priorities.
This philosophy does not address the values & priorities of your life, it assumes you already have those somewhat figured out. Practicing this system will assist you in refining them.
Deciding if you care takes effort. Oftentimes it's not as simple as we wish it to be. If you do not spend the effort to logically answer this question then emotion/instinct/habit will answer it for you, which is undesirable. The very nature of this question is to make a logical decision, however it's acceptable to answer because of emotional reasons alone after thinking logically.
This is a black & white question, do not allow yourself to provide a gray answer because simplicity is a core part of this philosophy. Make up your mind, it's OK to change it later, if justified. You are not prohibited from judging to what degree you do or don't care. Instead you must first answer the yes/no question, then decide to what degree you do or don't care.
Being upset, dwelling, or worrying about items you don't care about is prohibited. Of course this is easier said than done, however this is the goal even if it's not 100% obtainable. Being able to let go is important.
Receiving joy/value from items you don't care about is possible and encouraged.
By answering this question you decide what path you take in applying this philosophy.
If you do care, then control is important: it's a requirement for category 1, and without it you have category 3.
If you don't care, then control doesn't really matter that much because neither of those categories (2 & 4) are important.
Keep things in proportion. Deciding if you care after accidentally stepping on an insect (3 or 4) may not deserve an equal investment of your time/energy compared to deciding if you care about purchasing a home (1 or 2). Act accordingly when deciding how much effort to spend categorizing an item, yet also practice & refine your system when an opportunity arises.
There are an infinite number of scenarios life can present you, practice being flexible and open minded when developing your system. You can gain practice by imagining yourself dealing with other peoples' situations. It may not be enjoyable, but you can learn more about yourself.
I find it useful to decide immediately if I care, and call it my 'first reaction'. Then I challenge it.
If I do care then I ask myself "Should I not care?", and I sometimes take my time answering the question.
If I don't care then I ask myself "Should I care?"
I often ask myself "Will this matter in a year?" in order to better judge if I care.
I must identify the emotional part of myself weighing in on the question, in order to effectively answer it.
I often put this philosophy project on hold because I had to really think about the values and priorities in my life.
I recall the first day when I realized real progress had been made:
One morning I found my car's driver-side mirror torn off and the front fender scratched; somebody had swiped the side of my parked car. Of course my first reaction was emotional; I was upset, "Yes, I care, this is my car." Then I asked myself "Should I not care?", and then all of a sudden things became more complex. I had recognized my emotional response; it was obvious. I believed I cared because I was emotional about something of relatively low value.
So then I thought "It's just a cheap used car. I can buy a new mirror for the cost of a meal, plus I don't care about the scratch. I drive a cheap car for a reason. In fact, this is exactly why I drive a cheap car. It could have been stolen and it wouldn't matter in the grand scheme of things. Why am I upset? Why do I care? This isn't a category 2 item, it's category 4. I really don't care and I obviously have no control, thus I should let it go. Even though it cost me thousands, this is category 4."
Thoughts are one thing, but actions are another. Later that day I had completely forgotten about what occurred, and was quite surprised when I remembered the incident the next day because I noticed the mirror was still missing. It seemed I really didn't care, what is better proof of that fact than forgetting? I am certain I would have dwelled on the situation had it occurred a few years earlier, because I never would have questioned if I should actually care.
I was truly delighted that day; all my effort working on the new philosophy/habits had actually shown results.
The system worked for me. I had changed, it was undeniable.
Today, if my house burnt down and nobody was hurt I believe/hope I wouldn't care that much. I'm prepared for this scenario because the possessions I value most are old family pictures (1) and I now have digital copies of them stored elsewhere, and the home is insured (1). The home became a category 2 item even though it's the most expensive possession in my life. The home and pictures are easily replaceable.