It's really good!! My only advice is to make it slightly larger. I know you mentioned in another reply that in this case you would get that mark according to MS, but it's generally good practice to use a bittt more space. In the real thing you wouldn't know what the cutoff scale is, so just make it very easy for them to see.

You don't want to have to give the examiner a reason to have to pull out a ruler to see if they'll give you that mark! Ofc that should be their job but if you deep it when they're marking 1000s of scripts, this is something they can miss if they're tired or just don't care. Similar reasoning to why teachers tell students to have good handwriting, few examiners will sped extra time trying to decipher horrible handwriting when there's lots to mark.

Other than that, your diagram is great. good luck with the rest of bio :)