wow, i've never heard this rule before (that I can remember, anyway)
my general rule was
19 and under - 2 yrs plus or minus
20 - 23 - 3 years plus or minus
24 - 28 - 5 years plus or minus
i didn't really have a plan for if i got to 28 and was still single
28 - 33 - 10 years minus no plus
I didn't know there was a mathematical equation for dating.
Its the difference in age equation..
Ah, as long as they aren't jail bait you are fine. Hahaha
for some people its 16 - 35, 25 years plus or mins