Thinking about it a little more, I suppose for something like the flying toasters, the toasters were probably like 50x50 px sprites. 8 bit color per pixel. Maybe 10 frames of animation. So 25 kB, and add 5 kB for the toast sprites. And then 2 kB for the code, gives 32 kB for just the flying toasters. So ~40 different screen savers could fit on a floppy.
After Dark 1.0 for Windows comes on a single floppy and is 716k in total, compressed, before installation. After installation, the 34 different screen saver modules take up roughly 650k in total, for an average of about 19k per module.
TOASTERS.AD is one of the more advanced ones and is roughly 27k, so your guess is pretty close!
