Is this buffer being created correctly? about e-paper HOT 2 CLOSED

Your calculation is wrong. Assuming you are talking about the 1.54in display with a 200x200 resolution the calcuation is the following:
For y=0 && x=1:
(1 + 0 * 200) // 8 = 0
For y=1 && x=0:
(0 + 1*200) //8 = 25

For the floor division:
Each Byte of the image buffer contains the data for 8 different pixels, therefore you divide the "pixel position" by eight to get the correct position in the array.

from e-paper.

Oh yeah, my mistake; wasn't following the order of operations correctly in my head. Thanks also for explaining the image buffer 👍.

from e-paper.