Stinger and dive numbering in Log facility

I recently bought a stinger computer from a web based auction site.

Last Friday (06/01/05) I went swimming and wore my watch just so I can start
learning how it works before I use it "in anger".
I place it on the bottom of the deep end (2 meters) and left it there for
nearly a minute. It registered my "dive" and gave me all the relevant
information. Today I went swimming again (09/01/06), again I took my watch
and placed it on the bottom of the deep end for nearly a minute.

The second dive today has been registered with the same log number (-06) as
the "dive" I did on Friday, even though it has given me a SURF time of 72
hours between dives. Both are shown as Dive 1 (D 1) in the log display, both
show the correct date and time for the relevant dives. Neither "dive" is
showing a dive time as I guess it was too short to register. I was expecting
that the stinger would register them as separate dives due to the surface
interval being approx 72 hours and therefore allocate a different log number.
My understanding is that if the surface interval is less than 5 minutes it
will treat the dives as being part of the same log.

I have read and re-read the instruction manual and hope that I haven't missed
a really obvious solution to this question.

Hope this makes sense