Newby question regarding theme suffixes

When I downloaded a Ocadia theme from the WordPress 1.5 theme competition, it showed up in my administration page for managing themes (after I installed the files to my i-power v-deck)as Ocadia 1.0 , and the same thing happed for the journalized-winter theme.

Is it a 1.5 or a 1.0? Adsense Deluxe plug-in says it won’t work with anything less than a 1.5

Perhaps I am missing something in my understanding about those suffix numbers?
Thanks for any insight.