Script execution time

A quick question. In the functional limits there is:

Free: Script/code execution time (5 seconds)
Extension: Expanded script/code execution time (20 sec)
Extension price: $5/month

Does that mean 20 sec is the max, or you can buy an additional 20 secs for every $5 ?

Thanks

Currently 20 sec is the max, we will be adding additional function packs to allow further extension of the execution time.

I have purchased this pack but still i am getting 5 second error

What is your Application ID?