What is the time dilation ratio that Noriko and Kazumi experience? At the end of the anime Aim for the Top! Gunbuster, Takaya Noriko and Amano Kazumi must travel at sub-FTL speeds (that is, at speeds slower than faster-than-light) to reach from the epicenter of battle to Earth. 

What is the ratio of their time dilation? That is, how long has it been for Noriko and Kazumi versus how long has it been on Earth?
The center of the galaxy is about 8,000 parsecs away from Earth. The Gunbuster was heavily damaged while completing its mission, but was able to escape the black hole. However, they had to have spent at least 33 days at sub-light speed trying to outrun the blast while also trying to long distance warp back to Earth after finding suitable ethereal space for warp.

So 12,000 Earth years have passed. For Noriko and Kazumi only 33 days and a few hours had passed.