To push Radius attribute 25 as part of authorization for VPN users, following stpes have to be followed:

Step1:

Browse to Policy Elements> Authorization Policy> Network Access> Authorization Profile and click on create;

Step2:

Create a new authorization profile as shown in the snapshot below. Name of the new authorization rule is Radius-attribute25:

Step3:

Click on RADIUS attribute tab for the above profile created and add Class attribute 25 as shown in the below snapshot. ( In the snapshot,VPNgroup is the name of the group that has to be pushed as class attribute)

Step 4:

Click on Add and Save the config

Additional info:

After you create Authorization Profile, browse to required Authorization policy under Access Policies and assign the Authorization profile as a result to respective rule of authorization policy.