Quote from MTE:
The doubt comes from the fact that you cannot trade options without a basic understanding of them. Whether you're buying or selling them is irrelevant to that knowledge! So, given that you don't have a basic understanding of options, we have naturally expressed some doubt in your experience.
You've proven my point yourself by not being able to calculate your P/L from selling 115 put @ 25, getting assigned and then selling the stock at 91.
Exactly. It's irrelevant if you are buying or selling options. It's evident you didn't understand your risk when you entered into the trade. If you are EXPERIENCED in trading options, you should know what your break even point is.
As for earning a profit on this position, you have gained nothing until you close your stock position. If the stock falls to to $80, you have just lost $10 a share since your cost base is $90.
You really do need to read up on this and stop fooling yourself that you know what you're doing.