In Visual Basic, the decimal data type is known more commonly as "Currency". So that's probably why the control defauts to a mask with a dollar sign. You will need to set the InputMask and FormatString on each control to change this.
Set it to what?
I use "n2" as my format and "{double:-16.2}" as my mask.
"n2" simply means format the number with thousands separator and 2 decimal places.
"{double:-16.2}" means allow floating point input where 16.2 specifies the number of digits in the integer portion and and fraction portion of the value respectively. The "-" simply means allow negative values.
Standard Numeric Format Strings
Custom Numeric Format Strings