Welcome, Peterb.
To adequately light a space it's easiest to use a standard power density. HID lighting(HPS, MH) will need about 50 watts/ sq feet of floor space. Leds can be a bit tricky trying to estimate their efficiency at converting power into light. Older tech diodes common in the fixtures you've purchased are at best equal to HPS lights so the same 50w/sq ft rule applies. When you step up to current tech diodes like those used in Quantum Boards, cobs or light engines can operate at 30w/sq ft to achieve the same light output. P.S. you need to know the ACTUAL power consumption of your light to determine how much area they can cover, not some imaginary marketing number.