You can find this behavior in your silverlight demo site. (http://demos.telerik.com/silverlight/#MaskedInput/MaskedNumericInput
I have specified a Mask of p9.2, and if you fill up all values in the input, you can see in the output that it has placed the decimal two positions to the left.
this only seems to happen to percentages, # seems to work fine.
I've attached a screen shot.
This also happens in my application.
I am using version: 2011.1.315.1040
Also just tested in 2011.1.419.1040
Ignore this, after reading the msdn documentation (http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx#PFormatString
) I now understand whats going on.