Hello, it is correctly converting - appearance of the light remains the same, only the numerical value changes. For example - directionality of Vray light 0.8 equals 0.56 in Corona Light after conversion. It is expected and could be the same with other values. For example - glossiness 0.5 could mean something else in Corona Mtl and in Vray Mtl.
Why would you like to have a ratio here?