The Baseband sample rate parameter on the SDR transmitter block is the rate at which the sample will be sent by the RF card, i.e. the sampling rate at the DAC. In your model, you have chosen 4Msps. This value is fixed and you must set up the rest of your design to provide enough data to the DAC.
In your model, you have created a source which is generating data at 100kHz (1/100e3), you then put it through an upsampling Rasied Cosine filter which raises the sample rate to 400kHz (where you have this data being sent to the transmitter at 100e3 in frames of 4 samples). So, you have a mismatch between your desired simulation parameters and what the hardware is expecting.
Even with that mismatch, however, Simulink does not run in synchronisation with the hardware, it just runs the simulation as fast as possible. The simulation needs to run fast enough to provide data at 4Msps to the hardware. In your model, you are working with very small frame sizes, which is very inefficient. If you enable the lost samples port on the transmitter block and add a scope to the output you will see that samples are frequently being dropped.
To make your model more efficient, you need to work with larger frames. Please see the attached model for guidance.