Sorry Mathijs, perhaps I have not explained my self very well. I was hoping to find out how the real world KR 87 tunes in to the 0.5K Khz frequency resolution, but have since found out that it cannot in any event.
There is no issue with the KR 87 fitted in the Aerosoft Twin Otter Extended,
In fact whoever programmed it did an amazing job because it does pick the 0.5 Khz frequencies.
P3D & FSX do infact simulate the 0.5 Khz NME frequency resolution which is peculiar to Europe only and is described in the CAA documentation Section 2.2.1 Applicable Standards EUROCAE document ED-51 [Ref 4]