This additional amount is computed using the PIOOYA (Pull It Out Of ...) method of high finance

We are not clear on how charges to the customer's CC card will work.
When the customer initially places the order their card is "authorized" for X $.
If we then subsequently change this amount during order processing does ABLE handle this OK - re-authorizing the amount etc?
Then when we finally ship the thing we assume the customer's card is charged the original $ amount plus whatever we had to charge extra to do the work for our customer.
Could someone help explain the way Able handles CC processing as it relates to after-the-fact additional charges?