Lush henna hair dye/how much

Hello! I got the henna hair dye from lush but I’m not sure how much I should use as my hair is very short!

Buzzed on the sides and back and about 2in on the top at the longest point. I feel like I will only need one square, maybe even just half a square.

Anyone with short hair who has used this how much did you need??

All the tutorials I’ve found are gals with really long hair so it’s hard to gauge how much I’ll need >.<

Thanks!!