How to add a second port forwarding rule on Comcast Business Gateway router

i am having trouble configuring port forwarding on an SMC Comcast Business Gateway router--and their tech support cannot figure it out.  Last week I got my first rule working by setting it up as follows:

Name    Public      Private     Protocol     IP Address

              Range      Range     

xFTP   21-21        21-21          TCP          10,1,10,242

Now I need to another rule so I key in:

xSFTP  22-22       22-22           TCP          10.1.10.242

But when I try to save this new rule I get this error:

"Public Port Range conflict with Remote Management Ports"

Does any one know how to add this 2nd rule for port 22 on this router?  TIA