Absolute error of the estimated envelope and core rotation rates for the evolved model. Left panel: Absolute error of the estimated envelope rotation rate as a function of the input core and envelope rotation rates. The input core and envelope rotation rates are given on the x- and y-axes, respectively. The error in the estimated envelope rotation rate, in units of nHz, is colour-coded and truncated at a maximum value of 100 nHz. Grey dots indicate the underlying grid of input core and envelope rotation rates. Contour lines are spaced by 10 nHz. Right panel: Same as in the left panel, but for the absolute error of the estimated core rotation rate. The colour scale is inverted because the errors on the core rotation rate are negative.