ok...
$10.00 to $25.00 the rate is $5.00.
$25.01 t0 $60.00 the rate is $10.00.
$60.01 to $150.00 the rate is $15.00.
Over $150.00 the rate is $20.00.
There are more ways to do this than one, but here is one using 4 rules....
Rule 1:
"Based on cart subtotal" >=10
"Flat Rate" 5
Rule 2:
"Based on cart subtotal" > 25
"Flat Rate" 5
Rule 3:
"Based on cart subtotal" > 60
"Flat Rate" 5
Rule 4:
"Based on cart subtotal" > 150
"Flat Rate" 5