We must make sure the process() function does not mark too many transactions as processed.

Each timestamp slot has limits for effort, which is fine, but the problem is also that one block may contain multiple timestamps (in case of block production slowdown).

So the process function must make sure that it doesn't mark as scheduled more callbacks than the limits on the collection, which are:

• default maximum number of transactions allowed inside a collection: 100 - 2 (existing system tx) = 98
• default maximum value for total gas allowed: 10_000_000 - subtract some buffer for 2 system tx
• default maximum value for a collection byte size: 3_000_000 - subtract some buffer for 2 system tx