We've found an issue when masking a negative number using FPE1ext. When masking a negative number whose length is equal to the field's maximum length, an error is returned.
Here's an example of an error when masking a NUMBER(2,0) field whose value is "-19"
Masked value too wide for column, Masked value -19, Column: VAL, Function: FORMATFPE1EXT, Table column width: 2
Release : 4.10
FDM counts the negative sign as part of the value and fails on the comparison as it compares 3 (the length of the value, but in fact should be 2) and 2 (column width).