There is no simple answer.
First question is what meter did that person use? If it was a low cost meter from lets say Home Depot and made for lumber measurements, the percentage means nothing in absolute values. I suspect that one of those lower cost meters was used to get those values which would indicate a very wet hull.
The proper procedure is to use a fiberglass specific model of meter.
If the boat was hauled just before the measurement, the readings may be way off.
If the boat was on land for a long time, the readings may also be off.
The meters can not read moisture through bottom paint. If readings were made on bottom painted areas that were not scrapper to bare gelcoat, the reading are garbage.
Frozen wet structure or hollow rotten areas like transoms will read perfectly OK but aren't.
The readings from multiple spots should be compared to get relative readings from likely wet area as well as typically 'dry' areas.
A thorough tapping of the hull should also be formed to identify delaminated or hollow areas and compared to the moister relative measurements.
Moisture measurements are tricky and in general, just one tool for surveying a hull.
