Exclusions based on AV signatures

Hi Team, 

I am facing a false positive issue for a AV signature for a custom batch script used for automation and send by microsoft SCCM to their clients. Fortigate is setting between the server and the client. The customer wants AV scanning to work for all the files sent from the Server to it's client but want to disable a particular signature which is firing. 

Can someone guide me in how we can create an exception for a particular av signature from av scanning. 

Sebastan