JEE Advanced 2024 Chemistry question on Aldehydes Ketones and Acids

An organic compound P having molecular formula $\text{C}_6\text{H}_6\text{O}_3$ gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of $\text{NH}_2\text{OH}$ to produce oxime Q. Treatment of P with excess methyl iodide in the presence of KOH produces compound R as the major product. Reaction of R with excess iso-butylmagnesium bromide followed by treatment with $\text{H}_3\text{O}^+$ gives compound S as the major product.

The total number of methyl ($-\text{CH}_3$) group(s) in compound S is _____.