fix two off by one errors

[kmatch98]

Yikes! Found two off-by-one errors in my last commit on Bitmap.blit.

Lesson: Do way more testing prior to next PR request.

[jepler]

Fix how many off by one errors? 😁

I didn't test it, but the changes make sense intuitively.

[kmatch98]

Good question, whats the right function to use for counting off-by-one errors (can I pick the last one?)

• 1+1+1+1
• 2*1^2
• 1^4