Left: Simulated luminosity of an ultra-stripped supernova (blue dashed line) and observed luminosity of iPTF14gqr (white points). The ultra-stripped supernova rapidly fades through shock cooling for three days after the explosion. Then later, at five to ten days after the explosion, the supernova brightens again because of the decay heat from radioactive substances produced in the explosion. The observed luminosity matches the predicted luminosity very well. Right: Simulated spectrum of an ultra-stripped supernova (white solid line) and the observed spectrum of iPTF14gqr (pink solid line). The spectrum of a standard supernova is also shown with a blue solid line for comparison. Many elements of the spectrum of iPTF14gqr, from the overall trend to the fine features of the absorption lines, coincide well with the simulated spectrum.