Byte 2 is the NDEF size byte, and while 6D is the normal and suggested size for NTAG216, it does not fully utilize all physical user memory of the chip, but for … reasons … NXP chose 6D as their capability container size for the NTAG216.
A value of 6F is not standard, but should not cause any actual usability problems unless you push your data size to the limit, then it may (I would have to calculate this) push into the configuration bytes… but that problem can be averted if you can get your chip protected… which I see from your ticket you have tried but receive an error.
Can you post the full scan data of chip, or at least blocks E1 through E6?
Also what app did you use on your iPhone to get the raw tag data with?