[TEC] What does this mean?

[Jolierouge]

F2Sargo, 1 means there`s one boat of the specified class available.
In data/roster/whichever nation/submarine there are *.cfg for each class;
my example is taken from JHapprich`s Alfa, which has six predefined units.

So F2Alfa, 3 would mean three random units from that list are available and one would be assigned to you, making the ID of that boat a random name or number.