What does 3-volume and 6-volume means?

[everlastes]

I saw these in a chemistry workbook in my school:
5ml of 3-volume hydrogen peroxide solution ..., 5ml of 6-volume hydrogen peroxide solution ...

What does 3-volume and 6-volume means? The problem is about rate of reaction and concentration. So the notation should have something to do with concentration.

Thanks

Rosetta Stone Italian