Resistance (%) question

There is 75% (89%). What does 89% mean?

That's the amount you have ignoring the resistance cap. Useful mostly for making sure you're overcapped enough to mitigate the effects of resistance-lowering curses.

It means you're wearing enough stuff or have buffs etc to be at 89% resistance, but the game caps you at 75% so that's your effective number. You must have taken a node on the skill tree that raises your cold resistance cap by one, so cold is allowed to make it to 76%. You haven't hit the cap yet on lightning resistance, so there's no adjustment.

sometimes it is useful to have overcapped resists. for example fire resist when playing Righteous Fire build or to not oneshot yourself on reflect when cursed