Will It Make a Difference on Low Setting?

Six years ago I had 5 fraxel restore to improve acne scars, texture. It made a fantastic difference and I was delighted. I have just had a top-up. I had the session 2 hours ago and am still red and swollen but I can still the mild discoloration I wanted to erase. I asked my doctor not to set the settings too high. He said they were average ( I think he said 40)and he could 'gone way higher' Should I have let him or will the discoloration fade when skin peels. Or have I wasted my money?