Confused about signature size

In the list of rules here the maximum size for a signature is given as 150 pixels high by 640 pixels wide. When I go to my User CP to upload a new signature, it says the maximum size for my custom image is 100 X 500 pixels. I thought I had finally gotten the signature thing figured out, but now I'm totally confused. Which format am I supposed to be using?

I think custom image and signature are two different things. Your signature is usually a link to the image being hosted on an outside site. The custom image is if your using an image stored on your HD. In this case, I think that the image is then moved to TCS and so they want it smaller so it takes up less space? If it's only a link (using the top box) then the file space being used is that of the image host and NOT TCS.

Meaghan is correct, if stored on a TCS server they have to be smaller as they must be within the upload guidelines but you can save to photobucket and link to an image that within the sizing rules of 640x150 and 30k)

Thanks for the information.

Now I have another question. If I make a signature for someone else, should I keep it to the 100 X 500 pixels size?

I usually make them at 550 x 134 which allows them to have a line of text. 99% of people are hosting the photos you see to make sigs with so they have somewhere to host them and those that dont, I have just left on my own photobucket with a note not to delete