This is a theory. Years ago a sub. Coordinator showed me my job screen and it showed jobs for that district and other districts I sub for. From researching, reading, talking/listening to subs, I believe the sub. Coordinator when he needs to fill jobs he will take off jobs in Aesop for some subs, so they do not see those jobs on aesop.
EXample, let's say there is a school called Morton high school. Usually only 8% of the subs sub there. Let's say there are 10 jobs available on monday. 3 of the jobs available for Monday are Morton high school jobs. Since only 8% of the subs will sub at Morton high school, the sub coordinator will only show the Morton high school jobs to the 8% who sub there. The sub coordinator will not show the other 7 jobs on Monday to the 8%, why? Because she wants all the jobs filled for that day. Sub coordinators get pressured to fill all the jobs for that day. That's why they call subs sometimes. I believe this happens once in a while and only in some districts.
The jobs show up on Aesop a online sub. teachers website. If a sub works for 3 districts that have aesop, all The jobs available will show up for those 3 districts on aesop. The sub. Teacher picks and chooses what job he wants on aesop. Some subs only work for one district