Question about diaper sizing?

So this may sound a little dumb, but boxes of diapers that say size 1-2 does that mean there is a mix of sizes 1 and size 2 in there or is it a different size all together that is in between sizes 1 and 2? Im hoping its the second, My daughters in pampers and shes too big for the size 1s now but the size 2s are too big on her and leak everywhere