Disagree - this is being told only half the information that you need to know and not 'equivalent to a typo'. The W/Wh typo is common enough, but being given only the power output of a storage system is useless at best, misleading at worst - it could be the mother of all supercapacitors, capable of 10GW for a few minutes, or it could be something more useful that is capable of returning 10GW to the grid for several hours (or preferably days) at a time.
From what
@Bald Rick says, it would be up to 20GWh of storage (around half an hour's UK consumption at time of writing), and whilst the "one/two hours at full power" holds true currently that limits their use to flattening peaks of demand, it doesn't really solve the more concerning "long period of reduced generation output" scenario which we can still cover with thermal power stations at the moment.