I have to analyse 1261 rows by the first 4 characters of their post code (zip code)

So let's say the column values are:

RM7 0AH
RM14 1BB
RM14 2XX
RM6 1PQ

I want an output as below:

RM7 1
RM14 2
RM6 1

I've tried googling but can't think of how to describe what I'm looking for