Looks like an airspace restriction notice, I fly around airports all the time and get similar warnings, don’t forget climb corridors can extend a long way along the extended centreline of many airports.
It does sound like a DJI GeoFEnce restriction but it shouldn't be an issue because we ALL fly at or below 400' AGL anyway
What area was this in? Have you looked at any FAA maps to determine Airspace issues? It may or may NOT have anything to do with legitimate FAA Airspace but you'll want to check and confirm that.
Check DJI's Geo Map. "Altitude Zones" aren't types of legally restricted airspace, but are safety zones DJI codes in that typically extend off the runway centerlines from nearby airports. You should see them on the map I linked above in shades of gray.
Get it every time I fly at my favorite location. Don't go above 400 feet...so not an issue. Rarely go above 1 or 200 feet. I also get the confirmation to take responsibility for my flight, and do have to keep an eye on the plane pilots that like to come down and buzz the bay.