Greetings from Syncfusion support.
You want to cut-off the integer part of the NumericTextBox based on the provided format but the behavior and usage of custom format (#) is different. The # custom numeric format only formats the numbers with group separators, decimal separators and round off the decimal digits as per the number of # present after decimal separator and it will not touch the integer part. Please refer the below documentation on custom numeric format,
The custom format for our controls have been implemented as per the MSDN standards. Please refer to the below documentation,
If you really want to limit the numbers present in the integer part, the MaskedTextBox is the recommended one which uses mask configuration to limit the display digits. Please find the below documentation on Mask Configuration of MaskedTextBox,
We have prepared a sample based on your requirement. Here is a code snippet,
<ejs-maskedtextbox mask="000.000" promptChar=" "></ejs-maskedtextbox>
Please check with the provided information and get back to us if you need any further assistance.