Yea I know, you have to be very careful with this program.

Also note they should have something like this on the auction.

Please DO NOT PAY instantly. Win the item (s) you wish to purchase and then please wait for a combined shipping invoice. Paying instantly produces a super quick turn-around and nothing can be added to an already paid invoice. So again, please DO NOT PAY instantly, wait for a combines shipping invoice All issues are first prints, in high grade near mint condition. Please ask any questions. YES, I do combine shipping so please do not pay instantly

If they don't then hit them up about it.

Also yea the program doesn't combine postage on seperate purchases, so make sure all items are checked out and combined.