Manage backup sets

I'm using Macrium Reflect 5.3:

My ext hdd has 4 sets

01-02-15
01-04-15
12-31-14
12-25-14

I would like to delete all except 12-25-14. Do I delete from within Macrium?

Also looking at c:\user\rico\documents\reflect

I find 8 references to dates, and only one, has a date, that's on the ext hdd (12-25-14). Do I just go there and delete?

After this I'll use the manage feature in Macrium

Thanks