BinEdit uses two scales to measure the location of verticies. They are: editor units and feet.
 

Aside from the apparent awkwardness of using two different scales inconsistently, this actually has two great advantages.  The first is that it provides a bench mark on which we can compare the size of models in BinEdit to the size of the terrain in mtm2 (and the other games).  The second is that it allows a high degree of vertex location accuracy when editing a model.
 

Using the scale

For example, if you want to make a square block building that is four stories tall.  We know from real life that most buildings average about ten feet per floor.  So, our building will need to be forty feet (4x10) in total height.

Doing the math.

Since our scale is 1 foot = 256 editor units, we need to multiply 40 feet (our target height) by 256 which gives us a building height of 10240 editor units.
 

Now, models like this function best if they are centered along all axes.  This means that half the height will be above the x-axis and half below it.

Doing the math.

To maintain our height, we must divide by 2 (we're dealing in halves, right) which gives us 5120 editor units above the x-axis and 5120 units below it.  Please note that the vertex point below the x-axis will now be indicated using a negative sign (-5120).
 

We are now ready to enter the Y values to "add vertices" for our building.  The top of the building will use a Y vertex value of 5120 and the bottom of the building will use a Y vertex value of -5120.  The building will be a perfect forty feet tall.

Now, go ahead and calculate the vertex values for width and length/depth.
 

Accurate vertex location

It is very difficult to provide a random example of using 1 / 256 of a foot.  At this point, just let me say that this is helpful when:

- moving parts in relation to a larger bin
- lining up two verticies with pin point precision
- defining shapes and curves using fragmented pieces
- joining the seams of two faces

One thing should be clear, however, which is that making models is all geometry, and geometry, of course, is all math.  Have fun.