Funny how I start finding answers after I ask the question, regardless of how much research I do beforehand.
I found the ONTAPI docs in the 4.1 Managability SDK (I can't find the same in the 5.2 version).
According to the doc for the volume-info API:
|snapshot-blocks-reserved|| ||integer||The number of 1024 byte blocks that has been set aside as reserve for snapshot usage. This is same as "blocks-reserved" in snapshot-get-reserve API output. Range : [0..2^64-1]. |
This is the only value given in blocks. All of the other values are in bytes.
So, all the examples I have seen where people are converting this value to GB, they are actually converting it to TB and adding it to other values in GB.