Why is my MacBook Air's battery percentage decreasing every 3-4 days after a recent replacement?
[Re-Titled by Moderator]
MacBook Air, macOS 15.0
From what I can understand from the information posted, it does not appear to be abnormal. If you have reason to believe something is wrong, you should definitely contact Apple regarding its replacement. Authorized repairs are guaranteed for a minimum of 90 days.
Refer to If your Mac battery runs out of charge quickly - Apple Support.