hi,
this type of transaction is a 'pending charge', they will submit a
$90 charge when you fill up your car at the pump with a credit card,
send a charge for the actual amount and the $90 charge will
disappear in 24 hours or so. If you pay at counter this is not done.
This explains it a lot better then I can
http://en.wikipedia.org/wiki/Authorization_hold73 james