This is standard stuff. It means they get to charge you interest on the money if you don't pay them. The "highest rate permitted by law" just means that they can set what they feel is a reasonable rate in this situation without being challenged on it legally.
If you are concerned about it, send an email to billing@hitechcreations.com and ask for clarification. They are very responsive.
You should also be aware that you can pre-pay. Print the form out from the web site and send them a money order, that way you can't ever go "in the hole" so you won't have to worry about it.
------------------
Lephturn - Chief Trainer
A member of The Flying Pigs
Visit Lephturn's Aerodrome for AH news, resources, and training data.
http://users.andara.com/~sconrad/"MY P-47 is a pretty good ship
And she took a round coming 'cross the Channel last trip
I was thinking 'bout my baby and lettin' her rip
Always got me through so far
Well they can ship me all over this great big world
But I'll never find nothing like my North End girl
I'm taking her home with me one day, sir
Soon as we win this war"
- Steve Earl