Bafang BBSHD set wheel diameter?

Hi,
I have a Bafang BBSHD (with a C965 display unit) installed on a fatbike. Problem is I cannot find anywhere in the settings where I can set accurate wheel diameter. I have a 26", but a 26" fatbike tyre is larger than a standard 26" wheel and the speed shown on the display is 10% - 20 % lower than actual speed.

Does anyone have a solution for this?

I wonder if setting the wheel diameter to the next size up, you would get a truer reading?

Go into password protect section:

https://www.greenbikekit.com/media/...e95/c/9/c965a-manual-8fun-bbs01-bbs02-kit.jpg

Then set the wheel size to the next one up. Maybe even two:

https://www.greenbikekit.com/media/...5/c/9/c965a-munual-bafang-bbs01-bbs02-kit.jpg

Set it to the setting that is closest to the tirediameter, do a test and compare to GPS speed, and correct as necessary.

My "26 inch" fat tires are more like 29 + but some can be bigger again.