\begin{tabular}{@{}r@{g }lrr@{ = }r@{}}
\toprule
\multicolumn{2}{c}{\thead{Ingredient}}& \thead{Percentage} & \multicolumn{2}{c}{\thead{Calculation}} \\ \midrule
1000& flour             &100\%        & 1000g of 1000g & 100\% \\ 
 600& water             & 60\%        & 600g of 1000g  &  60\% \\ 
 100& sourdough starter & 10\%        & 100g of 1000g  &  10\% \\ 
  20& salt              &  2\%         & 20g of 1000g  &   2\% \\ \bottomrule
\end{tabular}