I have been tasked with incorporating a new system into an existing boundary. My ISSO told me to go through NIST 800-53 and review and check if any of the controls are impacted by the new system.

I am not sure what the criteria is for this? He said- does this control "change" with the new system. I am looking at it from the perspective of- Does the new system use this control? If so, how? and if it's not applicable to note that.

The communication with this ISSO is terrible so I am afraid to ask more questions. Any help is great!