Not sure by what you mean by “sponge”.
I posted the definition. You're getting the air or whatever out faster buy pumping out the gas you put in with it.
Get the vacuum as low as you can then break vacuum with the refrigerant up to 0 psi. Then re-evacuate. Repeat once more and then do a deep vac.
12Psi suction. Have no idea if that is good. I was used to about 30Psi on mobile AC
Don't even connect the two! They have totally different operating parameters. Do you have a pocket P/T chart? That'll tell ya whether you're close. Off of memory for 12 you're somewhere around 0-5* But wait and see where it settles out and note the compressor shell temp over time. You'll want to shoot for a +20* evap so press. is around 18-20 psi with a frost line on the suction about 6" from the compressor. Cap tube systems take time to settle with each charge adjustment.