Short version: 1000 milliamps per hour or 10 % power cell charge per hour. A typical phone will cost 30% of the battery and a typical small device will take about 10%.
Long version:  it takes 10-12 hours of sun charging to charge the battery from depletion in full sun. We recommend you Sun Charge 4x longer than discharging as a general rule. If you use it as designed to charge 1 phone or just a small device you can keep the power cell full more dependably.