A few million. Also known as the difference between the minority and the majority. Seeing as you’re not talking about voters but about how many people actually agree with Trump, that makes a difference.
The only silverlining is that Trump is unlikely to get 8 years. There were a good number of people that voted for Trump because they didn’t want to vote Clinton or didn’t want to leave their party. That’s likely to change as they realize the consequences of their votes.