Red underline when spell check is turned off

[morningscifi 1]

Hello,

I often write measurements in different notes, like for example:

2 tbsp 5 lb 10 kg

And letter/number combinations like 5x12kg.

It has been bugging me that the app underlines these in red, as if they're misspelled. I have auto-correct on my device turned off (and even tried turning off the English dictionary entirely) and still my notes are filled with red lines. Any way I can turn off the app's spell checking?

[Milincho 20]

Same here. What's up with that?