People focusing on the excel error and rebuttals such as this one are missing the point. The R/R argument fails because the causal inference itself is bunk. There are few plausible reasons to believe that higher public debt --> slower growth, but many reasons to suggest that slower growth --> higher dGDP. Public debts are private sector financial assets, and they are the result of deficits that represent a net flow of income from the government to households. The risk there--excessive inflation--is almost the opposite of the one suggested by R/R.

However, if the economy stalls and GDP growth slows, that leads to lower tax revenues and higher transfer payments (unemployment, etc), which will contribute directly to the deficit.

The level of confusion one sees in most any discussion of government debt/deficits is really mindblowing sometimes.