The current timetables are different from yours:
http://iwamigroup.jp/publics/download/?file=/files/content_type/type01...Departures from Odashi Station:
6:52, 8:47, 9:37, 10:52, 11:22, 12:42, 13:02, 13:42, 14:52, 16:27, 17:37, 18:37
Note that the 6:52 and 18:37 departure does not operate on weekends and national holidays.
In the opposite direction:
Departures from Omori-Daikansho-Ato:
7:07, 7:43, 9:31, 10:56, 11:34, 13:26 13:57, 15:07, 16:13, 16:32, 16:53, 18:07
7:07, 16:53 and 18:07 don't operate on weekends and national holidays.
16:32 does not operate on weekdays.
All but the first two and the last departure of the day start their journey from the Wor;d Heritage Center about seven minutes before departing Omori-Daikansho-Ato.