Sprite size much bigger than originally - how to resolve

I rendered out a sprite sheet animation that contains 98 pieces of sprite images and the whole folder's size is 26 MB. I imported them to use as a sprite sheet and the profiler says the textures take up 380 MB. I don't have anything else in the scene except for those. As for one piece of them, 272 KB is one sprite's size according to the Windows Explorer and it is 1.6 MB in Unity with the mip maps turned off. Is there a way to get around this and dim down the texture size?