Rimuru, the protagonist of That Time I Got Reincarnated as a Slime, has powerful magical abilities. In that world, "magicules" are basically particles of mana and are the fuel for magic. In two episodes we see him depleting magicules to below his minumum reserve point, at which point he shuts down for three days. When he awakens, his supply is fully restored.
In episode 3 he names about 100 goblins and, lastly, the direwolf alpha. (Later we learn that naming the alpha (Ranga) allowed the name to be shared by the entire pack.) Then he shuts down due to insufficient magicules. In episode 6 he names about 500 more goblins before shutting down. Even if naming Ranga counted as 100 named wolves, that was still only 200 total beings named the first time.
Could he actually store about 2.5 times more magicules after about 10 days? That is the simplest explanation for the greater feat. If so, is it known if his magicule storage continues to grow at that kind of fast pace?
A second possibility is that, in the first instance, simultaneously affecting a whole pack acted as sort of a short circuit on magicule usage. Doing it one at a time might have used much less total. This case would not require the kind of magicule storage growth seen in the first.
A third possibility is that as he learns to use his abilities, he gets more efficient in using them. So the second time he could accomplish a lot more with the same amount of magicules.
A fourth possibility is that I'm way overthinking this...