If you convert the original Okumura-Hata formula (Hata´s report) into the format of the planning tool you can see exactly what k1 and k2 are. It took me 2 pages of paper. Basically the original formulae operates with km and MHz, and the planning tool is using meter. So, you put a factor of 1000 and convert the formula. Than you find the values for k1, 2, and so on.