Let's get this math done. We have 815 and we're going to multiply it by 4. This is the same as taking 815 and adding it to itself 4 times.
Step 1: 0 + 815 = 815
Step 2: 815 + 815 = 1630
Step 3: 1630 + 815 = 2445
Step 4: 2445 + 815 = 3260

So, 815*4 = 3260