A kilowatt (kW) is a rate of power. Chargers are rated in kW - for example a 7.2 kW home charger or a 60 kW DC charger. A kilowatt-hour (kWh) is an amount of energy: the energy delivered by 1 kW flowing for one hour. Battery capacity and electricity bills are measured in kWh, which is also what DISCOMs call a unit.
To estimate charging time, divide the energy needed (kWh) by the charging power (kW). Adding 30 kWh at 7 kW takes a little over four hours, plus some allowance for losses.