What does ppm/K correspond to?
5ppm/K means that the resistance will change by 5 parts per million per 1 Kelvin change in temperature.

The datasheet for your resistor should give the baseline temperature, but it's probably 20C (roughly 293K).  So, if the temperature of your resistor is actually 300K (27C) then it's resistance will be 10 * (1 + (7 * 0.000005)) = 10.00035R.