How do I find how much space is remaining on my repository?
Do you mean available disk space? Just check the disk space in windows, or SAN application that hosts your repository.
Or do you mean space until the next rollover volume is created?
Laserfiche does not (normally) limit the size of the repository other than hardware and SQL or Oracle limits. SQL Express is limited by the built in limits of the SQL Express instance. Full SQL and Oracle have limits too, but they are limits of the hardware and computing.
If you are using Avante for SQL Express, it is still impossible to put a document count on it, because the DB size is the limitation, and the DB is effected by fields, annotations, if version controlled, etc. so not every document adds the same amount of data to the DB.
For harddrive space, again, each document will contain different amounts of data so you cannot get a hard figure of X documents = Y GB on HDD.
What is the whole question that you are trying to answer and maybe you can get a more specific response.