Breastfeeding

Hi mommies, I've been exclusively latching my baby for a month. My baby now is 7 weeks, latch for 10 mins each side and every 3 hours. Yesterday i am curious how much breastmilk i can produce but i am only able to express 20ml on each breast. I was able to express 60ml each breasts previously before i exclusively go on latching. Does it mean my milk supply have went down? And my baby only have 40ml each feed?