There is a limit of 20 activity-batches that can be loaded into any schedule.
Most people use only 6 to 9 Batches.
It is not a good idea to use lots of small Batches.
The reason for this is that if you have a Batch of only a few lessons then you are not giving TimeTabler the opportunity to work on your data and suggest a priority order to you.
This is because TimeTabler can only prioritise the activities in the Batch(es) that is currently loaded.
So if you have a Batch of only 6 lessons of Year 7 then it will only prioritise those 6 lessons against each other(!) ...but of course you want to know the priority order of all the lessons in Year 7, in order to assign all of Year 7 in the best sequence for a 100% fit.
So most people have one 'Fixed Points' Batch, and then either one Batch or two Batches for each year-group.
eg. one Batch for all of Year 7.
eg. two Batches for Year 9: one for the big blocks (which I know in advance that I want to assign first) and then the other Batch for the rest of Year 9, etc.
In this way, you can guide or steer TimeTabler by the sequence in which you load the Batches progressively into the schedule (as explained in Section F9 in the Manual).
Click here for a discussion of the best sequence to load the Batches.
See also steps 20-22 in the QuickStart Guide in Section A of the Manual.