Numeric non decimal column returns decimal value
When you create a custom numeric column with a setting of 0 decimals in a list, the SharePoint interface lets you to introduce decimal values and it rounds the number after saving. So if you type 1.5 it will be rounded up to 2.
From my point of view, it shouldn't allow to enter decimal values like 1.5, but this is not the "real" problem.
The real problem is that when you retrieve that column value, you will retrieve a 1.5 instead of the 2, which is the value you are seeing in the list using the interface.
This needs a fix since from my point of view it is a bug and it is causing many problems because of the examples I gave above.