It's given in kWh/month/m2. To obtain the total energy harvesting of your module, multiply this figure by it's power rating (as they are rated for 1kW/m2 incoming radiation power)*. So for a 1Wp (Watt peak) panel that you leave outside in the sun during the whole daylight time, you can expect ~50Wh per month to be produced in October, ~180Wh in June, and maybe ~15Wh in December. A full charge is 8Wh, plus about 20% charging losses (rough estimate) you need 10Wh to charge your battery.