It’s likely that your seqeuence is not the same setting as you source material.
try this….
take a source clip and drag it down to the new Items button at the bottom of the project panel.
this will make a sequence that is the same setting as the source….
then see if if your monitors match.
BEYOND THIS…its important to understand that your sequence needs to be set up to give you a clear path to the type of material you will ultimately be delivering.
but that’s a longer conversation….
Alex