For surface injection, Fluent injects at each face centroid, but that doesn't mean that your parcel count is limited by the number of cell faces. Please check the different parcel release method in the manual (constant mass, number, etc...) What Ive just explained is valid for the standard method.
For steady particle tracking, the particles are tracked from injection point til final state, but you can still vary the number of tries.
Bsides when using RR distribution, there's the input 'number of diameters'.
Please go through the manual for more details on particle treatment.