Force Carb a Strong Scotch Ale 9E?

[Annunciation_Dan]

I'm looking around and finding volumes in the 0.75 - 1.30 range recommended, except every online calculator is giving me negative values for PSI. is this beer supposed to be flat or am I missing something?

 

[Quetzolcotl]

Brewing Classic Styles says to carb to 2 - 2.5 volumes