A resistor and a capacitor are connected in series to a 10 V de supply through a switch. The switch is closed at t=0, and the capacitor voltage is found to cross 0 V at t=0.4τ, where is the circuit time constant. The absolute value of percentage change required in the initial capacitor voltage if the zero crossing has to happen at t=0.2τ is _______ (rounded off to 2 decimal places).