OK, let's work through this together. We're starting with 255 and we're going to multiply it by 4, which means we add 255 to itself 4 times.
Step 1: 0 + 255 = 255
Step 2: 255 + 255 = 510
Step 3: 510 + 255 = 765
Step 4: 765 + 255 = 1020

So, 255*4 = 1020