The number attribute when try to save the value with 20 9's '99999999999999999999' then the value saved as 9,223,372,036,854,775,807
Steps to re-produce:
1) Open any number type attribute.
2) Enter 20 times ‘9’ digit 99999999999999999999, then click on save.
3) It is showing the value as 9,223,372,036,854,775,807
Release : 15.8.1
Component : CA PPM APPLICATION
Development has labeled this as "Not a Defect" because it is due to a Java limitation on the number size.
If you have a business case for why you want to use that large of a number, you could submit an idea through your company representative for the PPM Ideation process.