Hi Sadak,
The bin size is a relationship between RBW and the window function used. For most of our processing, we use a variable flat-top window to achieve the desired RBW.
The saBandwidthClamped warning will get returned during saInitiate if the RBW had to be changed to fit within the limitations of the device.
We have a list of the RBW limitations in the user manual here, under section 2.3.1, many of them are related to center frequency and span. This manual is for the SA44B but applies to the SA124 as well.
https://relatedcontentdemo.kinsta.cloud/sigdownloads/SA44B/SA44B-User-Manual.pdf
If you have follow up questions, let me know.
Regards,
A.J.