A resistor and a capacitor are connected in series to a $\text{10 V dc}$ supply through a switch. The switch is closed at $\text{t = 0}$, and the capacitor voltage is found to cross $\text{0 V}$ at $t=0.4\tau$, where $\tau$ 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 $t=0.2\tau$ is _______________________ (rounded off to $2$ decimal places).