If you have a million dollar umbrella and 100-300 on your auto insurance is your total coverage one million three hundred thousand?

It depends on your policy.

Your liability coverage for an accident that doesn't involve your car is a million because of that umbrella policy.

For an automobile accident, your total coverage is probably 1.3 million, but might be less because of an exclusion in either policy about duplicate coverage. That's not a common exclusion, though it is possible.

It depends upon your policy. You should have received a copy of your policy when you paid for your coverage. If you don't have a copy, or don't understand it, call your agent or insurance company.