Those numbers are with full sunlight. You will not get those numbers in practice for most of the year in most places. First few reviews seem to say they were getting around 4 watts from the panel. I'd expect closer to 10W-12W assuming hte manufacturer is honest.
I mean, you can just buy two in that case. Each one is like 27mm only.. so, fairly easy to carry still.
Or buy double the power one.. they still comes in pretty much the same form-factor. Example: https://www.amazon.com/FlexSolar-Portable-Waterproof-Emergen...
^ This one is 100 watts.. still costs less than $100.