The power limit will depend on the type of load on the GPU. Different games and benchmark suites will load down the GPU more or less than others - I see this all the time on my 2080Ti. It's most common when comparing Furmark to say, Unigine Heaven - Furmak will limit the GPU clock to a lower rate due to how it's taxing the GPU, where as Unigine will run peak clocks. This is similar to how Intel CPU's can't run full clock rates running heavy AVX instruction sets.
Tip - You can use GPU-Z's sensor graphs to tell you what is limiting you GPU's performance 😉
Tip2 - If you really, REALLY want to go nuts, you'll have to modify and re-flash your GPU's BIOS to go beyond the 115% limit. It's doable, but I don't recommend doing it without a TON...