I was confused before with build no. And its versions no. I have found out that the only way to know the corresponding build and os version numbers is to listen to the news everyone every time a new update is released.
Here are some:
Build 10051= OS 12534.56
Build 10052= OS 12534.59 (current)
Build 10072= OS 12555
Build 10080= OS ????? (coming soon)