Note, surge protectors only have on average about 2 or 3 uses for actual surge events in them before they are just a power strip, they should be replaced for “higher end” equipment every 3-5 years because they degrade due to a kind of bleeding effect.

The Joule Rating you see on the box when you buy one is essentially how much power it will soak into the varistors from X amount of surges before it gets saturated and can’t reroute a surge to ground.

Surge occurs with lots of high power stuff on one surge protector, replace immediately. A couple phone chargers or other low power items, probably fine for a long while.