There's no mention of times for September on their website. However, they run throughout the year and it would be wise to either ask the driver, ask at the dolmus station or ask at whichever restaurant you're using in Kabak.
From Fethiye : 07.00 - 11.00 - 17.00 (April-May )
From Kabak : 08:30 -12:30 - 18 :30 ( April-May )
From Fethiye : 07:00- 09:00 -11:00 - 13:00 - 16:00 - 18:00 ( June-July-August)
From Kabak : 08:30 - 10:30 -12:30 - 14 :30 - 17 : 30 - 19 :30 ( June-July-August )
