The schedule is a guideline rather than a hard and fast rule. The principle you are following is to confine the puppy when you can't be there, so they are less likely to have accidents. If you suspect the puppy needs to toilet then remove them from the crate and put on the toilet area. If they don't toilet within five minutes then return them to the crate. Or, if the puppy cries in the crate and you think they need the toilet, wait until they are quiet and then pop them on the toilet spot.