I’m probably not much help because I’m one who generalizes sins. The priest has no problem with it.
Let’s say I have a problem with sins of thoughts against certain people, I know that I’ve had disparaging or negative unloving thoughts about these people. Let’s say I work with this person and once again I get a rotten unloving thought about that person several times a day. Now add those nasty thoughts to several times a day, give or take 5 days a week (some days are nicer than others). Add to that the thoughts after work on a bad day, there’s no way to know how often I’ve committed the sin of not loving my neighbour.
If I have a problem similar to this type, I will tell the priest outright that this is a recurring theme in my life against certain people, and if I’ve been working on it, but still fail, I’ll tell him next time that it’s getting better because I’m trying harder but it’s still a problem that I carry with me.
Often as well, I have a bad memory, there’s no way I can count the number of times I’ve done certain things unless they really stick out. The priest hasn’t had a problem with it.
Personally, although it says in number, I think they want that because then the priest can figure out which of your sins are a big problem for you. They can then figure out the best penance for you and if time allows, advise you on your worst sins.
Number also keeps a penitent more honest with himself and the priest, but if someone is going in with an open and honest heart I don’t really think numbers are as important.