The pill is deemed missed if it’s been 24 hours after the moment you should have taken it. A single missed a single pill or a start of the new package a day earlier isn’t dangerous as you are still covered. But if you forgot to have two or more tablets or started a new package 2 or more days later it can affect your coverage.
If you skipped a tablet, follow the instruction that comes with the pills. If you still don’t know what you should do, use supplementary protection methods and consult a gynecologist.