Add "15" value in "Cron throttle" setting.

Please, add "15" value in "Cron throttle" setting.

Example.
I have 2500 users.
Gmail limit = 500.
If I set 20: 20 * 24 = 480 letters - so close to limit, but I should send another letters (registration, password forgot...).
If I set 10: 10 * 24 = 240 letters - I will send all newsletters in 10 days :)

15 rules!