In the axial position, the methyl group experiences steric crowding (steric strain) because of the presence of axial hydrogen atoms on the same side of the ring (known as the 1,3-diaxial interactions). There are two such interactions, with each pairwise methyl/hydrogen combination contributing approximately 7.61 kJ/mol of strain energy.
In the axial placement, the methyl group faces spatial obstruction (steric obstruction) due to the presence of axial hydrogen atoms on the same side of the ring (1,3-diaxial interactions). This results in two such combinations, with each contributing approximately 7.61 kJ/mol of strain energy.