Pumping Stats

Morning

I am currently 15cm NBPEL and 17.5cm BPEL.
After 20 minutes in the pump at 6-7HG I am 18cm.

My question is whether 18cm is what I could achieve in the future. If it is then my goal should be to get to 18.5cm in the tube and this may push my BPEL to 18cm. I know it may not work like that and I may need 19cm in the tube but is that the rough way gains work for those that have had them using the pump?

My intention is to pump for 20 mins Monday to Friday for a month and keep checking my PI’s.

Thanks