At low frequencies the phase is Arg[-20]/Degree-90 = 90 which is what is seen on the BodePlot.
You may desire that the phase of -20 be considered as -180 degrees instead. In that case just tweak the PhaseRange .
BodePlot[(4 (s - 20))/(s (s + 0.8)), PlotLayout -> "Phase",
PhaseRange -> {-((3 [Pi])/2) - 2 [Pi], -((3 [Pi])/2)}]
