You're given 100% "RadiationImmunity" stat over 1 second, that means it just fills that stat.
Then the stat itself decays over 10 minutes on its own, see Stats.sbc and docs at wiki RadiationImmunityStat Definition[spaceengineers.wiki.gg].

I suspect they did it with a stat instead of a consumable effect (using the Time) because that prevents other consumables, would kinda suck not being able to use anything for 10 minutes, and I also guess they also don't want to change the consumable deny thing so here we are xD

Regardless, I do need to do something about that printout as it is rather misleading, I'm thinking for positive Value I can show how long the stat takes to decay (also positive there), and similarly if both value and decay are negative for the opposite effect (consumable reduces it, stat increases over time on its own).

I also have a WIP thing to show more character-specific stats next to the buffs window, which will also show that RadiationImmunity stat and how long it has left and etc, so I could also hint at that in the consumable tooltip... not sure yet, we'll see.
Thanks for the report!

Thanks, all-mighty wizard Digi.
It is truly a blessing that you continue to contribute to this community.

Welp bad news, MyRadiationImmunityStatDefinition is not whitelisted so I can't get the decay rate... I might need to just remove the "Consumable:" section, vanilla has tooltip with relevant stats on theirs and modders can do the same so probably not even needed anymore xD

well..... that's bad but yeah... tooltip contains relevant stats descriptions so deleting consumable section is actually a option to choose I think.

anyway, thanks :D