I just put 35 Designers on my Suspension. Next Model column said 24 May 2015. Then I hit save, still 24 May 2015.
Then I refreshed the page suddenly it said 23 May 2015!
Toggling to 36 Designers and back to 35 it says 24 May 2015 again.
Seems like clientside calculations in JS differ from serverside code. Maybe a float issue.