Sorry to hear about your dog Steve, sounded like she lived a long life.
Actually, the 7 year figure not really correct. Dogs (and cats) mature quickly at first and then level out.
6 months = 10 years
1 year = 15 years
18 months = 20 years
2 years = 24 years
3 years = 28 years
4 years = 32 years
5 years = 36 years
6 years = 40 years
7 years = 44 years
8 years = 48 years
9 years = 52 years
10 years = 56 years
11 years = 60 years
12 years = 64 years
13 years = 68 years
14 years = 72 years
15 years = 76 years
(and so on)