The Japanese version consistently says that it's actually tens of thousands of light-years instead of the original just thousands. So the high end of the old calculation is actually multiple times lower than the new low end.
Low end: 20,000 light-years.
Mid end: 50,000 light-years.
High end: 90,000 light-years.
'll treat the Galaxy like a cylinder to find it's volume.
This source says that it's about 100,000 light-years in width and about 1,000 light-years in height.
The formula to calculate the volume of a cylinder is π×r²×h(height).
π×50,000²×1,000 = 7,853,981,633,975 light-years³
To calculate the volume for how much space Gothitelle is warping, I'll use the formula to get the volume of a sphere, which is 4/3×π×r³.
4/3×π×20,000³ = 33,510,321,638,291 (low end)
4/3×π×50,000³ = 523,598,775,598,298 (mid end)
4/3×π×90,000³ = 3,053,628,059,289,279 (high end)
This puts the average Gothitelle's passive spatial distorting capabilities to being about 388.8 times greater than the area of effect of the Milky Way, making it only only 2.1 times weaker than baseline Multi-Galaxy level. This scales to any fully evolved Pokémon and should put Mega Evolutions and fodder Legendary Pokémon at Multi-Galaxy level, making their other Multi-Solar System level feats just further supporting of the Galaxy level rating.