An organic compound P having molecular formula $$C_6H_6O_3$$ gives ferric chloride test and does not have intramolecular hydrogen bond. The compound P reacts with 3 equivalents of $$NH_2OH$$ 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 $$H_3O^+$$ gives compound S as the major product.

The total number of methyl ($$-CH_3$$) group(s) in compound S is ______.