Iphone 12 screen time doesn't work properly

Understanding Screen Time Graph (Grey Bar explained)

All apps have been assigned to certain categories in the Screen Time. Screen Time has chosen the top 11 categories and has put all remaining categories in a category called "Others".

There are 12 Categories in Screen Time

1. Social: FaceBook, Hangout, Instagram
2. Games: Scrabble, PUBG
3. Entertainment: Netflix, Amazon Music
4. Creativity: Photos, Google Photos
5. Productivity & Finance: HDFC Bank
6. Education: SkyView, Learn Python
7. Information & Reading: Kindle, NDTV
8. Health & Fitness: BeatO, Health, Activity
9. Utilities: Voice Memos, Measure
10. Shopping & Food: Apple Store
11. Travel: Maps
12. Others: Big Basket, iTunes Store

The graph displays the top 3 (Time used by the user) category legends on the X-axis. Anything other than these legend categories is a Grey bar in the graph

For example:

If the user has used Social Networking, Reading, and Others category apps for the maximum time during a time span. The graph will show these three categories in the X axis as legends and the remaining categories (Remaining apps that have used less than 6 min account for what is being shown in Grey Colour.

The Bar Colours in the pic below are...

Blue Colour: 1. Social

Aqua Colour: 7. Reading

Orange: 12. Others (All other Apps not categorised under the 11 categories)

Grey: Other than Blue, Aqua, and Orange (2, 3, 4,5, 6, 8, 9, 10 and 11)

The highest usage is always Blue, the next is Aqua and the least reported usage is Orange irrespective of category reported

See the pic below explained

Background App Refresh can contribute toward Screen Time if the app is performing tasks in the background and its activity is associated with the user’s account. Here's how it works:

1. When Background App Refresh Affects Screen Time:
   1. Active Tasks in the Background: If an app performs visible or measurable activities while in the background—such as streaming audio, downloading data, or syncing content—this activity may be logged as part of Screen Time.
   2. App-Specific Behavior: Some apps are designed to run background processes that can register as usage time, especially if notifications or updates trigger interactions (e.g., opening a notification).
   3. Battery Usage Insight: While not directly related to Screen Time, you can check Settings > Battery to see if certain apps are consuming power in the background. Apps with heavy background usage could overlap with Screen Time reporting.
2. When Background App Refresh Doesn't Affect Screen Time:
   1. Passive Background Activities: If an app simply refreshes content or syncs data in the background without a user-visible impact or interaction, this activity generally isn’t included in Screen Time.

To verify if Background App Refresh is influencing Screen Time:

1. Tap on Show Categories (Shown in blue font in the Screenshot posted by you) Shown in the pic below
   1. 
2. Check the specific category usage details.
3. Compare it with battery usage stats to identify background activity discrepancies.

If you notice unintended increases in Screen Time, disabling Background App Refresh for specific apps via Settings > General > Background App Refresh can help control it.

Look at the pic below a cut-out view of your screenshot from your post.

Total Screen Time is a (Grey) + b (Grey) + c