So baby clothes come in NB, 0-3, 3-6, 6-9 etc. BUT some clothes I have just say 3M or 6M. Do the 3's count more towards the 0-3 sizes or the 3-6? 6's more towards the 3-6 or 6-9? I'm trying to figure out how many of each size groups I have so I know what more I need. Also, idk how many of each sizes to get to start out with. Onesies, just shirts, snap shirts, gowns, sleep n play zip up outfits. Did you have a guide you went by or something? FTM, thanks!