SlicerAxis in Execute response

Hi,

I'm confused as to the purpose of the <Axes><Axis name="SlicerAxis">
in the Execute response.

If my MDX statement is:
SELECT
{
Measures.[Order Quantity], Measures.[Sales quantity]
}
ON COLUMNS,
NON EMPTY
{
Product.[Product Name].&[228]
}
ON ROWS
FROM [My Cube]
WHERE [Customer].[City].[Birmingham]

then my understanding is that [Customer.[City].[Binmingham] is my slicer 
axis. However, the response returns every possible tuple in SlicerAxis
from 
the cube. This is confusing me. I thought that the contents of <Axes> 
relates directly to the returned <CellData>. If it should be anywhere, 
shouldn't it be in the <OlapInfo> rather than the <Axes>?

Ken