Dawn, BTW, if you use the search feature in this forum, you will sometimes get your answer more quickly if thre issue si a common one.

In this case, searching for the words "manual" and "zero" turned up the following post that covers this exact issue:
http://www.softrak.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=001750#000001