Using FormatFPE1 or FormatFPE1ext to mask a TINYINT data type fields will cause the masked value to exceed the upper limit allowed for TINYINT data types. We see this when masking tiny integers between 200 and 255.
Release : FastDataMasker all releases
The functions are working as designed.
Use WHERE conditions to mask the lower values (less than 200), and mask separately the upper values (200 and higher), but only mask the last digit.
NOTE: This also applies to other integer data types, since this is all about exceeding the maximum value allowed for the data type. For example, for the Integer data type, the maximum value is 4,294,967,296, so you would need something like a value of 4,xxx,xxx,xxx to eventually overflow the integer data type.
This behavior also applies to the FORMATENCRYPT* functions