Hi.
When you run the initial setup of myCRED the first time you activated the plugin, you are asked to set how your points should be formatted. This includes how many decimal point (if any) you want to use.
As pointed out in the installation guide, this can not be changed once you have finished the installation. Right now the only way to change this is to deactivate myCRED, delete the plugin via your WordPress admin page (and not via FTP) and then re-install myCRED with the new format you want.
Deleting myCRED via the WordPress admin area will result in your log and all your users points being deleted from your Database. If you just delete the plugin files via FTP you will leave your myCRED data in your database and this data will be used again if you re-install myCRED at a later point.
Of course if you feel comfortable with PHP and SQL you can write a script hat updates your log table, myCRED preferences and your users balances to reflect your extra decimal setup.