Weight for "Priority Mail" different than weight for "First Class" when shipping same item

Here are two labels from the last week (redacted to protect the guilty)

Nothing is being modified or typed in by hand, and “buy bulk shipping” is what it clicked to produce a set of dozens of labels at a time, all (one assumes) based upon the specs associated with the ASIN under “weight”, which is set to 11oz.
In both cases the product and packaging are the same