ATC would appear to have been following the 7110-65 which has an example not unlike this one:
EXAMPLE
The aircraft is en route to Delta waypoint at 6,000 feet. The
MVA for this area is 4,000 feet. “Cross Delta at or above
four thousand. Cleared M-L-S runway one eight
approach.” (See FIG 5-9-3.)
I agree it is ambiguous. Perhaps someone can check if they can access ATC recordings, but I suspect that the 'at or above 7,800' is a routine addition to the transmission for aircraft in the area with MVA of 7.800.
I would think that, as the aircraft was not being vectored the MVA should not be referred to at all. But that is not what the 7110.65 says.