Radiated emission limits
You can't "convert it", there is a reason why that's how the standard is specified. 

If you assume far field applies (at 10m it is barely at the edge of where it might start to become a valid approximation but at 5m it definitely isn't), then you can simply assume a power decrease with the square of the distance. That is you will have 4 times the power closer to the source (20dB).

In more general case you would use the Path Loss equation:

\$ L = 10 * n * \log_{10}(d) + C \$

Where n = 2 for free space far field (what I stated above) but it can be as high as 6 for near field.

There are other considerations such as the characteristics of the measuring antenna and also other requirements such as the conductive surfaces around the equipment.

The most you can do is to get a qualitative idea of what is going on, not a quantitative one. You can use this to compare to actual testing to standards and correct as as appropriate.

The far-field approximation becomes more and more valid as you increase the frequency. So you can get a better approximation on that section of the table.