Restriction code R1 is applied (internally to TISs and journey planners) when a 16-25 railcard is used. If the fare is discounted by a 16-25 railcard, then the minimum fare must be applied if you travel on any train that departs before 10:00.
So, if you want to travel on the 09:51 you need to buy the minimum fare version of the ticket, i.e. priced at £12. If the ticket is priced less than £12 and you're using a 16-25 Railcard it will not be valid on the 09:51.