RF Bandwidth and Sample Rate in TES

Hello,

Our PHY uses an OFDM signal of 20 MHz (from -10 MHz to 10 MHz) and works with a sample rate of 20 MSPS (complex I/Q samples). I've tried to set up a matching profile with TES, but the latter indicates that the configuration is invalid when I set the Dataport Sample Rate to 20 MSPS and the RF Channel Bandwidth to 20 MHz in the Device Configuration tab for the Rx1/Rx2 parts:

My questions are:

1. Should the RF Channel Bandwidth be set to the full signal bandwidth (from the lowest negative frequency to the highest positive frequency) or only the positive frequencies part (10 MHz in my case)?
2. If the answer to the previous question is the full bandwidth, why using a complex sampling rate equal to the RF bandwidth is not enough? Is there a formula that gives the minimum Navassa sampling rate for a specific RF bandwidth?

Thanks.