Q. What is considered germination?
Remove the crabgrass (all the roots), just covering the crab grass with mulch will not control the grass. You need to remove the crabgrass and its' roots with a shovel before you put any new grass seed down. Put new, bagged soil down where you have removed the old rootfilled soil then you can distribute new good grass seed down on the new soil. Keep the area slightly damp to promote grass growth. As an alternative you could go to Lowe's in Plymouth Meeting and by sod by the foot to fill in the area where you have removed the crabgrass. It is important to make sure that the seed or sod doesn't dry out or that it is drowned out. It's late to seed an area and it is easier to put down sod at this point. Germination is when you see that grass seed has sprouted from a seed to an actual leaf of grass.