The two digits
The first digit covers dust and solid particles (0 to 6), the second covers water (0 to 9K). IP66 means fully dust-tight and resistant to powerful water jets; IP69K adds hot-water high-pressure cleaning.
Hose plus gland is one system
The stated IP rating only applies when hose, gland and lock nut come from the same system and are tightened correctly. A cheap gland on an expensive hose drops the whole chain to its weakest point.
Mind the mounting direction
Never let a hose sag horizontally into a connection point: water collects in the lowest bend and creeps inside along the cable sheath. Mount with a drip loop below the connection point.