It's a color space metadata tag and of no real importance if you are simply importing images into FCP for grading and re-exporting into whatever color space you want. I've not used the Blackmagic iPhone app and I don't know if there are other options for tagging exports but I doubt it will matter. You are shooting Apple log and FCP should have no problem handling that.
The 9-2-9 tag basically indicates a Rec2020 color space (the 9s) with an undefined transfer function (the 2). Resolve uses these tags when exporting video and the most common ones are 1-1-1 (Rec709) 9-16-9 (Rec2020 P and 9-18-9 (Rec2020 HLG).
As W. Raider mentions, there has been and continues to be a lot of confusion about color space metadata tags and gamma shifts when exporting Rec 709 video from Resolve and how these files are read by FCP and Quicktime as well as problems when uploading to YouTube. Check out the Resolve forum if you want more info but prepare to be completely mind-boggled.