The above made no sense to me I always assumed that -15 +/- 6dBFS was a PASS
Turns out I’m wrong, a different test is used for different hardware, which makes sense, and for the LimeSDR-mini (and the LimeNET-Micro), a PASS is defined by the range -14 +/- 6BFS (-8dBFS to -20dBFS).
So to me it looks like your LimeSDR-Mini about 1 dB outside of the design specification.