noun which may take the genitive case particle 'no', na-adjective
on the large side; slightly larger; a little big
Describes something that is somewhat larger than average or expected, but not extremely so. Often used when choosing a size or describing a fit.
この靴は少し大きめなので、中敷きを入れています。
These shoes are a little on the large side, so I put insoles in.
大きめのサイズ
You'd better choose a slightly larger size.