How many eggs depends on the age and size of the female and the available nutrients when she was growing the eggs. I am not familiar enough with this species to give you actual numbers, sorry.
Most females mouthbrooders hold for about 21+/- days. Some species (like frontosa) can hold up to 6 weeks. It will also depend on how vulnerable she feels in the main tank.
If you are planning on keeping the fry you will need to move her before she spits. Doing on day 17 or 18 will make sure she doesn't spit in the tank and at the same time if she reflex spits in the net the fry will be old enough to survive on their own without special equipment like an egg tumbler.
Move her earlier if she appears to be taking abuse from other fish in the tank.
If you are not planning on doing anything with they fry (and she isn't being harassed too much) you can just let her spit in the main tank. A few fry may survive, most will get eaten.