Hey Mike,
I apologize, try file contents like this instead.
904.0, -250, -60
905.0, -250, -60
905.0, -250, -40
907.0, -250, -40
907.0, -250, -60
908.0, -250, -60
This specifies a minimum as well for each frequency. This displays correctly for me. It appears the two value line is not being parsed properly. This should resolve the issue and allow you to use limit lines.
Let me know your results.
Regards,
A.J.