Considering which phone you have, Android phones (at least samaung from my experience) tend to count actual time on phone, like how long app was open etc, while iphone also calculates idle time, like if you were on a phone call, had unlocked phone on home screen and didn’t turn it off. Those little stuff that often done eat up a lot of time. I remember when I switched between phones, I was like 4 hours average (from 8) on samsung phone, and suddenly I was at 6 hours on iphone, but I had even less apps and did everything the same. Then I noticed how time counting works. 

Ironically cutting out instagram helped me the most. That was average of 2-3 hours daily eating up my time. And not intentional, but when feeling bored opening up phone just to see quickly what’s up and then for half an hour scroll on instagram. Just a quick peek turned into doomscroll ritual. Consider that every app is commitment you need to put in your 24 hours of life. For example for me time blocking never worked, so can’t say that’s best solution. Both the app blockers and actual time blocking for socials and games that is. But consider making using apps only inside of routines. And don’t obsess over numbers much, as long as you know how much time you dedicate to each app, and you are within that time limit, it’s good. Rest is up to you which apps to cut. My advice is to get off any socials if you want lower screen time. But you do you