[CRITICAL] [PERSISTENCE DATA ERROR] [STABILITY] I got this error message for my private code

I printed custom data I save to a string ( JSON-like, with spaces brackets and commas ) and then got the size of the string.
I then added a string of the same length in the notepad and saved. It took only 47.4K which is 2-3 times smaller than the limit we are allowed (per docs it should be 128K)

Is there a hidden limit for some types of data?
Is limit for LEGO maps different?
Is some additional data added along with the data I want to persist?
Has the limit changed?

Also, I logged this suggestion: [REQUEST] Ability to get size of the persistable data in Verse

It would be cool if someone from the dev team could comment. @Flak