Ah, somehow I saw the 5-8 hours but missed the 1000mAh.

Still, I call it a BS. You can't escape geometry. The Sun bathes the Earth with about a kilowatt of energy per square metre. That thingy looks like it might be about 5cm across, giving us about 0.002 square metres to work with. At 100% efficiency this would give us 2 watts. Sadly, the most efficient solar cells available nowadays only achieve something between 15 and 20%. Let's be generous and assume 20%. That will get us to 400 milliwats. At full sunlight.

The battery in my N900 has a capacity of about 4500mWh (3.7V multiplied by 1210mAh - a to power status measurement). Assuming constant feed of 400mW we have so generously allowed above, it would take 11.25 hours of full sunlight to charge my phone.