That looks like a pretty fancy unit!
I see there is a button to select the range - if you get the correct one you should get a good reading - otherwise it is going to give you nothing useful - it will either bottom out at the low end or stick at the top end. Yes, it will read sunlight no problem - I'm sure of it. If you get the right combination of buttons pushed you should get some good numbers - did it come with a instructional booklet? Might provide some additional insight?