Let's roll up our sleeves and solve this. We have 255 and we're going to multiply it by 23, essentially adding 255 to itself 23 times.
Step 1: 0 + 255 = 255
Step 2: 255 + 255 = 510
Step 3: 510 + 255 = 765
Step 4: 765 + 255 = 1020
Step 5: 1020 + 255 = 1275
Step 6: 1275 + 255 = 1530
Step 7: 1530 + 255 = 1785
Step 8: 1785 + 255 = 2040
Step 9: 2040 + 255 = 2295
Step 10: 2295 + 255 = 2550
Step 11: 2550 + 255 = 2805
Step 12: 2805 + 255 = 3060
Step 13: 3060 + 255 = 3315
Step 14: 3315 + 255 = 3570
Step 15: 3570 + 255 = 3825
Step 16: 3825 + 255 = 4080
Step 17: 4080 + 255 = 4335
Step 18: 4335 + 255 = 4590
Step 19: 4590 + 255 = 4845
Step 20: 4845 + 255 = 5100
Step 21: 5100 + 255 = 5355
Step 22: 5355 + 255 = 5610
Step 23: 5610 + 255 = 5865

So, 255*23 = 5865