"500+ images" appears on a lot of photography price lists. It is close to meaningless, and occasionally it is a warning.
What the number actually measures
How many times the shutter fired, minus the obvious failures. It says nothing about how many frames are worth keeping.
A one-hour session can easily produce 400 exposures. Of those, perhaps forty are genuinely distinct — the rest are near-identical variations taken a fraction of a second apart, which is exactly how you photograph a moving child.
Why delivering all of them is not generous
It moves the editing job to you. Choosing between six near-identical frames is harder than choosing between six different ones, and most people never finish, which is how galleries end up unopened.
A culled gallery is a professional judgement about which frame in each run is best. That judgement is part of what a studio is for.
Roughly what to expect
A studio baby session: forty to sixty edited images. A cake smash across three stages: forty to sixty. A half-day event: a hundred and fifty to three hundred. A full wedding: six hundred to twelve hundred.
Those are estimates given in good faith rather than guarantees. A session that goes badly produces fewer, and padding it to hit a number would be dishonest.
Better questions than "how many"
Can I see a complete gallery rather than a highlight set? Do you cull, and on what basis? Are the delivered images edited, or is that extra? What resolution do I get?
Those tell you what you are actually buying.