If there are less "sending" characters in the data than there are "receiving" characters defined, the unstring will send the shorter number of characters (i.e. from the last delimiter to the end of data).
To better see how this works, i suggest you experiment by putting some code in your program and force various "sending" sets of data thru an unstring and look at the results after the unstring.
While the following is not exactly the situation you asked about, the link shows how the unstring operates:http://publibz.boulder.ibm.com/cgi-bin/ ... 0/220.127.116.11
If there are any questions about the info in the manual or if you have results that you do not understand from your experiment, post back here and someone will be able to clarify.