Can I change the numbers? or Should I delete the form and enter the numbers myself?

If you Auto-Filled and there was incorrect information on the slips, then you can edit the information on the slips or delete them and enter the data manually. Please be aware, though, that if you run Auto-Fill again, there is a change that the CRA may not recognized the edited/manually entered slips as the same ones that it has on file. In that case you may get duplicates.

what about the opposite problem: the slips have the right numbers but TurboTax ignores the slips and just shows $0.00. So I don't need to edit the info on the slips. I need to decide which numbers on the slips should go into the tax return, then change TT's $0.00 to my real income... Very weird inability to find numbers on the T4A etc to put *something* on the return.