NumericalAxis not ranging for very small values

I have a graph with very small time values (eg between 0.000005 and 0.0000055) and whatever I try as method to set the NumericalAxis (automatic or Binding Minimum and Maximum explicitly) the Axis keeps at 0 <-> 1.5 value and the graph is stuck on the 0 axis with no range to show.

It looks like a bug, since other (higher) values work perfectly fine, but I may be doing something wrong ...

Thanks,

Philippe