Free space on iPhone6Plus iOS 10.2.1 vs free space in iTunes 12.5.5.5?

[m4v3r1ck]

I'm still struggling to fully understand one of the most used core applications for the Mac, iTunes!

System
1. iPhone 6 Plus 16GB, - iOS 10.2.1
2. Mac Pro 5.1 - Mac OS X 10.10.5 & iTunes 12.5.5.5

Situation
After updating my iPhone to iOS 10.2.1 and my Mac Pro to iTunes 12.5.5.5, I have this - at least for me - very weird issue with a significant difference in the shown free space on my iPhone vs in iTune.

iPhone - has been synced with iTunes few minutes ago:

iTunes 12.5.5.5 - has been synced with my iPhone few minutes ago:

Questions
1. What could probably contain the "other" data for 609 MB?
2. What could probably contain the missing space for almost 1 GB on my iPhone that seems not claimed in iTunes?
3. When rebooting my iPhone I noticed that in iTunes the free space went up from 639 MB to now 1.2 GB? These maths drawn by my Apple ecosystem puzzles me to an extend that it's just mind blowing for me.

Thanks in advance for any help/direction to tackle 'my' issues!

Cheers

 

[m4v3r1ck]

Update

It looks like my iPhone's free space is slowly returning back to base from the iCloud. I let my 2 batteries - iPhone and Mophie Juice Pack - fade out untill the iPhone shut down, to let them be fully (0-100%) recharged again.

It's now at 762 MB / 1,32 GB that iTunes is telling me it should have. The "Other" section has doubled in allocated space from 609 MB to 1,36 GB

Ahh well, I'll just wait what will change in the statistics in the upcoming days. But if anyone could chime in here, that would be appreciated.

Cheers

 

[Mlrollin91]

For as long as I can remember, iTunes has reported differently than iOS. I don't know if its because of formatting and iTunes is reporting GB and not GiB, but unsure. Mine has roughly a 700MB difference.

 

[Shirasaki]

Mine has a discrepancy of 6 GB between iTunes reported free space and iOS ones. I also don't have a section called "other" at all. Instead, my "documents and data" takes a whopping 32GB of space.