The 500 credits that you show in your account are assigned because of your user level and are automatically used for your regular mailing. These will be automatically deducted and no action is needed. The space to enter credits is for additional members you want to see your message, so you would need additional credits besides the 500. Try clicking on an ad in members area... you can only do this once an hour, but you'll earn a few extra credits. Then go back and enter this number of additional credits... this is how many more members you'll reach above the 500!

Hope this is clear! Thanks for using The List Auction!