Sea level is also of interest as if it is very high this would increase the chance that many landmasses are separated by ocean and that more than one of them are designated as old world landmasses.
View attachment 688050
World mapscript remembers your last used settings.
So you are saying there is a minimum of 5 water plots separating your landmass from any other landmass, and that it is not the largest landmass on the map. This shouldn't really happen if one play with "old world start" (though it could theoretically happen, just very unlikely with most options being standard), but it is very likely to occur with start everywhere.