Sample rate in GRC

I am confused about the sample rate in GRC…if i am RXing a signal by
B210 at 2.4 GHz then the sample rate should be 4.8GHz??But USRP B210
uses a
direct conversion RX and shifts the signal to 0Hz,so what should be the
criteria for setting the sample rate?
Another option could be ton set it double the channel

If you want 1e6 Hz (1MHz) of receive bandwidth at a center frequency of
2.4e9 Hz (2.4GHz) then you just set the center frequency to 2.4e9 and
sample rate to 1e6 in the UHD source block in GRC.