Battery showing lower amperage

Civic coupe vti 99.

I have had my battery tested in Halfords and they said all was fine however they pointed out the amps on the battery was 263 whereas it should be 300.

I have been doing not 10 miles journeys so i would expect the battery to be ok. The guy told me maybe to go on motorway for a bit then come back and have it retested and it it was still showing that figure the battery would need to be changed.

What happens if the amps are showing 263 rather than 300 amps. Does it mean it will just not have enough cold cranking amps on cold days?

Can the lower amps lead to a car to cut out during driving for any reason?