Shipping flat rate by prices?

Just want to make sure I'm doing this right and won't create a loop.

Client pays taxes on items plus shipping. Wants to charge a flat rate...

Up to $1,000 - 20.00
$1,001 - 4,000 - 25.00 e.g.

So I set up the Rules for shipping
"Subtotal for Entire Cart Contents" as
If under <$1,000
"Based on the Cart Subtotal" Cart Subtotal Plus 20.00

"Subtotal for Entire Cart Contents" as
If >=$1,000
If < $4001
"Based on the Cart Subtotal" Cart Subtotal Plus 25.00

Is that going to be okay, or do I need to use "Based on a column's subtotal"
?

You should actually just use "flat rate" of $20 or $25... otherwise if you had $1000 order it would charge $1000 + $20 on top of the original $1000 for shipping for a total of $2020