Hi Oguz Unlu ,
To assist you more effectively, we have reviewed the reported issue by creating a simple ASP.NET MVC 4.8 sample using a partial view with the NumericTextBox component.
However, we were unable to reproduce the issue where the control appears smaller when rendered via AJAX. For your reference, we have also shared the working sample.
To help us investigate further and provide a more accurate solution, we kindly request the following additional information:
1) A reproducible sample or a modified of the shared sample that reflects your scenario.
2) The version of the Syncfusion package you are currently using.
Sample Link : https://www.syncfusion.com/downloads/support/directtrac/general/ze/PartialView-NumericTextBox
These details will greatly assist us in resolving the issue at the earliest. Please review the attached sample, and if you have any further concerns or queries, feel free to get back to us.
Regards,
Mallesh R