Because it does not matter where we restrict the number of votes to get the results we need, but it is often easier for a member to vote for more. If your stuck between 2 pics and not sure which to vote for and really don't care which of the 2 wins, we wanted you to be able to vote for both. The winner of the 2 would then be determined by other votes as yours showed no preference, but added 1 to the count of both.
This likely doesn't make much sense but statistically it makes the results more accurate and the voting easier.
The reality, we only 'plan' to use 13 of the pics for the calendar, BUT depending on the final results a collage created from a few pics is not out of the question. The most important part is that the pics on the calendar represent the wishes of the members. That is why we did not cull any pics this year and reduce the selection. The membership votes on the whole shebang!