Reproducing the issue:

1. create a Bamboo global variable under "Bamboo administration >> Build resources >> Global variables":

   Variable name	Variable value
   myVariable	itsValue

   

2. create a Deployment project and set a variable under "Deployment project >> Environment >> Variables":

   Variable name	Variable value
   myVariable	newValue Overrides global value: itsValue

   

3. create a new "Release versioning":
   
4. run your deployment:
   
5. in the deployment result you have: