Preparing spawn area: 0% each time

Whenever I load up my snapshot server instead of saying Preparing spawn area: x% and each time the number increasing until it reaches 100% it has 0%.
If it helps, I have a screenshot of the console output: http://prntscr.com/j5je6c
I have no idea why it does this and I assume it's a bug. It doesn;t affect the functionality of the server, just the console output. Thanks!