2-Methylcyclohexanone is treated with $\mathrm{CF}{}_3\mathrm{CO}{}_3\mathrm{H}$. Taking the migratory aptitude order secondary alkyl $>$ primary alkyl, the major product is

The more substituted ring carbon (C-2, secondary, bearing CH3) migrates in preference to the CH2 carbon (C-6, primary-like). Oxygen is therefore inserted between C=O and the CHCH3 carbon, so the lactone has the methyl on the carbon attached to ring oxygen: 7-methyloxepan-2-one.