Screen Time inaccurate data on my iPhone 14 Pro

If you feel an unauthorized person/app is remotely using, controlling or monitoring your device, then that is possible only if you have done one or more of the following Don'ts...

1. Don't hand over an iPhone to kids or to a stranger without Enabling Guided Access
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device
5. Don't give in to Phishing
6. Don't plug in your device in Airports and Public places through third-party cables and trust the device. Beware of Juice Jacking. (Especially in India)
7. Don't leave your iPhone unlocked and unattended in public places like offices, schools, malls, etc.

If one of the above is true then quickly change the Apple ID Password and Return iPhone settings to their defaults.

I am not sure what you are adding, and how you are adding.

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

Total Screen Time is a+b+c

In order to understand this better read this example below.

There are 9 Categories in Screen Time

1. Social Networking: Facebook, Hangout, Instagram
2. Games: Scrabble, PUBG
3. Entertainment: Netflix, Amazon Music
4. Creativity: Photos, Google Photos
5. Productivity: HDFC Bank
6. Education: SkyView, Learn Python
7. Reading & Reference: Kindle, NDTV
8. Health & Fitness: BeatO, Health, Activity
9. Others: Big Basket, 

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

For example:

If the user has used Games, Entertainment & Others category apps for the maximum time during a time span then the graph will show these three categories in the X-axis as legends and the remaining categories will be shown in Grey Colour.

The GIF below will illustrate the graph from 3 iOS devices

iPhone 6 iOS 12.4.5

iPhone SE iOS 13.3.1

iPad Pro 9.7" Wifi+Cellular iOS 13.3.1

Understanding Screen Time Graph (Grey Bar explained)

All apps have been assigned to certain categories in iTunes. Screen Time has chosen the top 8 categories and has put all remaining categories in a category called "Others".

There are 9 Categories in Screen Time

1. Social Networking: Facebook, Hangout, Instagram
2. Games: Scrabble, PUBG
3. Entertainment: Netflix, Amazon Music
4. Creativity: Photos, Google Photos
5. Productivity: HDFC Bank
6. Education: SkyView, Learn Python
7. Reading & Reference: Kindle, NDTV
8. Health & Fitness: BeatO, Health, Activity
9. Others: Big Basket, 

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

For example:

If the user has used Social Networking, Reading and Reference 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 remaining categories (Remaining apps which have used less than 6 min account for what is being shown in Grey Colour.

See the pic below explained