half power frequency seems unreasonable in example.c?

[ShepherdSosimple]

According to https://exstrom.com/journal/sigproc/dsigproc.html, half power frequency is 2*f/fs. So the input lower_half_power_frequency and higher_half_power_frequency seem not be to larger than 1.
Thus 2 and 45 may not reasonable in example.c line 9: BWBandPass* filter = create_bw_band_pass_filter(4, 250, 2, 45);