% chance to be opened again | % chance not to be consumed

% chance to be opened again | % chance not to be consumed for strongboxes\portals

What is the math behind those mods?
Does having 50% chance for portals not to be consumed in a long run means that out of 1000 initial portal uses, i would have 1500 instead?

Say you open 1000 portals.

50% of those will be consumed on the first go, and now you have 500 portals left. You've now gone through 1000 portals.

50% of those remaining will be consumed on the next go, and now you have 250 portals left. You've now gone through 1500 portals.

50% of the remaining will be consumed on the next go, and now you have 125 portals left. You've now gone through 1750 portals.


Continue the reasoning infinitely, you get 2000 portals on average. (This is called the Harmonic series by the way.)

Thank you!