Correct settings for rain with funnel (solved)

[WS Grave]

Hey guys, I use a funnel for my rain gauge.
One tip (which normally is 1.0 mm) is now 0.275 mm.
What setting (factor or offset) do I use for that?

/edit:
Found it (trial and error :)): set factor to 0,275 and offset to 0.000.
It now shows the good amount.