No, it's always 1 that is chosen randomly from the gems as the description says. The issue lies with the gem stats themselves. You have a socket type X and have a gem type Y. You want that specific Y to be kept, but that Y may not be the Y you see but some other Y1, Y2, Y3, Y4, etc.

Here's an example. A reagent that adds a modifier... I used it on an item with 3 gems that provide a 32-32 flat toxic damage bonus. Do you think I got toxic damage? Think again! I got 5% life leach from toxic damage.

I don't know how exactly the stat to be added/kept/removed gets chosen but it may be something entirely different than what you expect. People who report that their stat they wanted to keep still got removed ran into this issue. The game rolled something related to that gem, but it was not something that was on the item itself.

That was not quite what i was asking but thank you for the information. My question is more geared to removing unwanted stats, and keeping the stat you wanted via socketing the item with gem type that has that stat. For example u have an item that rolled crit, attack speed, Health, and health regen. From what i have seen on videos and reading you can socket that item with a gem that has crit as one of the modifiers, and the roll when removing the stat will protect that stat and prioritize the removal of other stats. I may be wrong there but if this is true i was wondering if u had multiple sockets could u socket a second gem in and it also protects a second stat.

I may have misunderstood some of the guides and read and watched and if that is the case i would appreciate if someone could inform me of the correct info.

I've already answered all your questions. No more than 1 stat is "protected" (or not even that 1 even if you have the right gems).

and if your doing that , roll off excesive slots , so you only have one , or you risk the RNG to pick a empty socket , and the gem is wasted and you will not achive the result wanted
ohh and for the first question , if it was not clear.. no..only one...