About the Radial distribution function

Hello. I calculated the Radial distribution function using GMX RDF, where I selected the same index group using-ref and -sel. Does it make sense to do so? After that, I made the result as shown, I do not understand the meaning of these two columns of data, I would like to ask, what is their meaning?
d8e34286cbc148b3d87da6061edba499