Danger: a real brand never does it
"Your channel will be deleted within 48 hours": a threat is never an offer
Restriction, deletion, a copyright claim, legal action: messages that threaten your channel to make you open a document come from scammers, not from YouTube or brands.
What it looks like
Remove your videos within 48 hours, or your channel will be deleted and legal action taken. The claim document is attached.
Why it is a sign
YouTube does not write to you that way: its notices are in YouTube Studio, never in a private video or an attachment. Fake lawyers, fake rights holders and fake "new monetization rules" exist to make you click out of fear.
What a real brand does
A real brand has nothing to reproach you with: it makes you an offer. A real claim on a video appears in Studio, with no file to open.
What to do
Open nothing. Check in YouTube Studio whether a claim or a warning exists. If nothing is there, the message is fake.