Original: They orbit each other with a period of 15.4 hours, which roughly indicates that the binary is very close — the separation being of the order of 10–20 km, if typical asteroid albedo and density values are assumed.
Simplified: It takes 15.4 hours to orbit each other, which says that the binary is very close — the separation being of the order of 10-20 km, if normal asteroid albedo and density values are assumed.