Statement:
But, if agent finished quest <<possible with other agent>> and started other quest <<possible with other agent>> simultaneously, you are to write first message about finishing, and second about starting.

e.g.

0001:01:01    Agent A finished quest 1.
0001:01:01    Agent A and agent B started quest 2.

or

0001:01:01    Agent A and agent B finished quest 1.
0001:01:01    Agent A started quest 2.

or

0001:01:01    Agent A and agent B finished quest 1.
0001:01:01    Agent B and agent C started quest 2.