What does ’25’ mean on this motorway sign?

Explanation: Before you set out on your journey, use a road map to plan your route. When you see an advance warning of your junction, make sure you get into the correct lane in plenty of time. Last-minute harsh braking and cutting across lanes at speed is extremely hazardous.

Category: Road and traffic signs

References: The Official DVSA Guide to Driving: Section 6, Highway Code: Page 110, Know Your Traffic Signs: Page 79