the value is being set correctly. the blcli_execute is echoing the 1st 'Example' and the 2nd is from your echo $PRIZMA_BSS_STATION_ID. so other than some ugly output, everything is ok.
you can try redirecting the blcli_execute stdout like:
blcli_execute <namespace> <command <args> > /dev/null
(unix) or > NUL (windows)
I just found the same question here: https://communities.bmc.com/communities/thread/39158
and I started looking for "redirecting output to null" on Windows when you saved me the search.