Errr? It's reminding you that you need a service soon (3 weeks / 21 days by the sounds of it), by 07/12. Isn't that obvious, or am I missing something?
No good waiting until the day before it tells you, that would be a bit inconvenient.
It's giving you time to get it booked in. Most people aren't as observant as you and wouldn't take any notice of the 07/12 10000mls bit.