OK, let's crack this. We're given 620 and our task is to multiply it by 4. Essentially, we'll be adding 620 to itself 4 times.
Step 1: 0 + 620 = 620
Step 2: 620 + 620 = 1240
Step 3: 1240 + 620 = 1860
Step 4: 1860 + 620 = 2480

So, 620*4 = 2480