Can the $Q$ factor of a system exceed unity ($Q>1$) while the maximum gain is 1?

when calculating the quality factor of an acoustic system using FWHM definition I get 39. the maximum gain is approximately (see the attached figure

).

when I calculate $Q$ in time domain using the formula (31) in the following article "Resonant properties of a nonlinear dissipative layer excited by a vibrating boundary: $Q$-factor and frequency response". I find 0.5.

I don’t know what I am doing wrong.
NB: by calculating I mean numericaly using MATLAB on data that I obtained from COMSOL