external Counter


i have a Zebra ZT230 in 'peel off' mode. Connected via USB for printing und connected via Serial for ZPL (e.g. printing information ~HS). I want to determine the number of labels which was really printed for an Program on an PC! I`m sending via USB one printjob with a batch of 999 labels. After a while maybe 100 labels are printed and the user want to end the batch. i`m asking the printer over the Serial with ~HS how many 'labels remaining in batch' and end the Job with ~JA. So ~HS will returned 899. BUT after peeling off the label number 100 there comes another label. One more label then i have counted. But in other random cases the counter was right. Exist there other way to solve this Problem? Have someone the same Problem?