If you want to charge:
a minimum of $0.08 for the first 3 minutes of a call and
$0.05 for each additional minute
Then, you should enter:

and

Example calls
3 minute call
3 * $0.0266666 = $0.08
minimum initial amount
5 minute call
(3 * $0.0266666) + (2 * $0.05) = $0.18
minimum initial amount plus additional minutes
1.5 minute call
3 * $.0266666 = $0.08
minimum initial amount