Yeh as '0' is the default but ive just tried it again.
This is on my 7.3b4 Test Forum from a clean install

But i remember the behavior is the same on my live 7.2.2
I have this and another topic running about custom islands,
the other could be related to a "Custom Header" issue with
a custom island.
But on this one, i'm trying to get the Custom Island to
update either every min, or every refresh.
At the moment it behaves as Static, where if i place
it anywhere else on my forum (not custom islands)
it will work off every page re-fresh.
Its a puzzler for me?
Even logging out and logging back in, it remains the same.
Didn't you have a similar issue where we thought it would
update after midnight? And it didn't ??