Baby clothes sizes - help!

I ordered most of my baby clothes from Carters. However, I noticed that their sizes are NB, 3m, 6m, 9m, etc.

I ordered from each size enough amount of clothes, but I’m wondering what about the months in between lol. Will the 3 months clothes fit up to 4-5 months? Or how does it work 😣

Sorry first time mom! Learning as I go.