My understanding is that they don't need it at all if they get only the game starter or similar feed. I could be wrong, but I'm new to this. I started out giving chick grit to my quail but they scratch around in and peck the dirt all the time in their enclosure so it seems pointless.
until you move them out of the brooder and as long as they are on starter mash, grit is not needed. Once on the grower food and out side grit is helpful to supplement what they find scratching around. Hope this helps.