That is if you upload one and use Adam's Forums as the server...
If you host it on your own website (or photobucket type site) it can be whatever size that you want for the file size. However, the graphic resolution is still asked to be within those sizes so that it does not overwhelm the pages.
And it is 976 KB, not 9.6kb
9.6 kb = 9600 bits
976 KB = 7995392 bits
It is not as small as you think...
My signature is a animated banner, and without look at the file, its roughly 3/10's the size of the maximum allowed as far as data size is required.