Compose numbers to 10 from 2 parts, and partition numbers to 10 into parts

What this means, in plain words

Partitioning means splitting a number into parts that add back to the whole, such as 46 as 40 and 6, or as 30 and 16.

Number work here is about how our number system is built, and about knowing what a number is worth rather than just how it is spelled.