OK, let's work through this together. We're starting with 512 and we're going to multiply it by 4, which means we add 512 to itself 4 times.
Step 1: 0 + 512 = 512
Step 2: 512 + 512 = 1024
Step 3: 1024 + 512 = 1536
Step 4: 1536 + 512 = 2048

So, 512*4 = 2048