A volume of manga an average has about 180-220 pages. A page of grey scale manga takes about 8-10 hours.
The question wasn't completely clear, so my answer may not be what you are looking for. That being said, I will tell you how volumes are 'made'.
As you may know, manga chapters are published in magazines on a regular schedule. An example of such a magazine is the Weekly Shonen Jump.
However, if a manga is popular enough, some of the individual chapters published in the magazine are collected and published into a single book. This book is a volume. Once there are enough chapters, another volume will be published.
Hope my answer helped you.