Ingress protection(IP Code) at connectors
Here be dragons!

Sometimes it describes the seal achieved between the connector and the case, but ONLY when the appropriate mating plug is inserted!

Sometimes it includes the unmated condition (Where the pins need to be sealed into the shell as well as the shell being sealed to the case and the mating connector being sealed to the shell when mated. 

An example of the difference is the two variants of the (Excellent) Souriau UTS series which are available either with push in contacts (only sealed when mated) or with factory fitted and expoxied contacts that are sealed in both mated and unmated condition.

"RS Pro" is radio spares own brand and tends to be a 'minimal datasheet' sort of thing, use someone else if you want proper data and for parts ordered a year or so apart to be the same. Basically the RS version of Farnells Multicomp.