When you purchase an APP your Credit total will decrease, you will not be charged to use the same app twice (as you will get an error messages saying there is no change) but if you undo that change and want to reapply with the APP you will have to pay to do it again.
Updating your car via any of the other coding options is free of charge if you have a PRO account but needs credit if you have a standard account.
OBDeleven Hardware and Software:
OBDeleven VAG Car Diagnostics App Free Download
How to Get Credits for OBDeleven:
The first time you log onto the application each day your front screen will show the following.
As you can see at the bottom of the screen you now get a new green line
This Message shows that you have had one Extra Free credit added to your
Account and if you want more hit the More button.
If you select the More button you will then be taken to an advert.
As soon as the advert loads you can do backup and your credit account will have increased by one.
When you have opened your first advert and return to open screen.
Select the main menu either by using the menu bar 
or by swiping your finger from left to right.
Now select Profile
From the Profile Screen select GET Credits and then Select Get free credit.
You can now watch another 4 adverts so in total you will get 6 credits per day
Once you have watched your maximum number of adverts the profile screen will have a new green message bar
see how many credits you now have your profile screen shows total number of credits
And the bottom of the screen also now shows how many credits
Please remember when you buy an APP this total will go down by the amount shown on the APP Screen.
Buy More Credits:
If you want to buy more credits then from the Get Credit Screen select 10 or 100 or 500 credits.
Hit the OK Button and you will get the following
Pay for the credits via your Google play account. Price correct at time of building page but subject to change.
Here are Two Case of OBDeleven Tests:
OBDeleven Perform Battery Adaptation for Audi A6/A8
OBDeleven VW Golf GTI 2013 Window Remote Coding Guide
UPDATE —- When you buy a new dongle sometimes there is a special offer that includes free credits.
To add these credits to your account select the Use code and enter the ‘xxx Credits’ code as printed on the bag the dongle was packed in.
Tap OK and that’s it your account will now be credited with the free credits you got with your purchase.