Those are
SINPO codes.
S (Signal strength)
The relative strength of the transmission.
I (Interference)
Interference from other stations on the same or adjacent frequencies.
N (Noise)
The amount of atmospheric or man-made noise.
P (Propagation)
Whether the signal is steady or fades from time to time.
O (Overall merit)
An overall score for the listening experience under these conditions.
5 is the best, 1 is the worst.