I read somewhere a 30 minute session consumes about 1GB of data, but don't quote me on this since I don't recall where i seen this number.
I am also assuming you are not testing this in North America?
I have always used Sandisk Extreme sd cards ,but then the Air 3s came into my life ,Out of 12 different cards none would work ,went to DJI for advice they now recommend (LEXAR ) bought 2 from Amazon 256 gb for 40 bucks bing bang boom They work...
I occasionally get that message with the card I always use in my Air 2S but the videos always come out fine. I'm not sure if it's a momentary hiccup or what but it doesn't affect what I'm shooting. It only happens once in a while.
I would recommend sticking to the well known brands such as SanDisk. As @mavic3usa mentions there are a lot of fakes around that not only fail to meet the SD Card standards set by the SD Association but also falsely report their speed and...