Time for RFE to change to 'RFE response Review'

HI, I would like to know how much time does it take to change the status from ‘RFE’ to ‘RFE response Review’ after you have submitted the RFE response. Does it change immedietely after they have received or it depends on the queue??

Also what documents to ask from the employer to confirm that he has sent the RFe correctly??