Where is this version number coming from, in my compiled CSS?

[badlydrawnrob]

I'm including a compiled file from devDependency, which is, in turn compiled using Less CLI.

The original project that's compiled:

The child theme that uses Print First CSS as a devDependency:

The question

In the last file, you can see a v3.2 but I've no idea how this is actually getting there. Could anyone enlighten me as to why this is happening?

It's actually quite useful and would be nice to version the Child theme also.