Milk flows out of boob after feed?

So this may be a weird question..but I've had issues with my supply, poor weight gain of baby and hence had to start supplementing with formula.

She has now regained her birth weight and put some on (due to the formula probably)

Recently have been having milk leaking from boobs. I have always compressed during feeds as thought I had a slow let down/low supply or lazy baby.

Anyway, I feed until my baby comes off herself. When I compress my boob after she comes off there is now milk still coming out, whereas before there would not be.

Does this mean my supply is finally increasing or does this mean that my baby isn't successfully "draining my boob"?

She is 4 weeks now. Feeds used to be more than 1 hour a time with her screaming after constantly. And now are about 35 mins with her nodding off occasionally after