Interesting I got almost the exact same reading on my Goal Zero 100w Panel. I assumed all 100 panels would produce about that much ( I am a noob) There was nothing wrong with my panel btw. Thanks for posting this info
The usual "power rating" of hobbyist panels is based on a sort-of-standard irradiation test usually conducted under unrealistic conditions of panel temperature etc. So, yes, it would not be surprising if you ended up with significantly less than nominal power even under very good insolation. And that's not considering companies that will flat out fake numbers of course.
What you will get out of '100W' solar panel is very dependent on what is actually hitting the panel surface. So, your latitude and time of year has a LOT to do with it. Obviously how 'clean' the air is will impact what hits the panel surface too. The more atmosphere (higher latitude (in northern hemisphere) and further from summer solstice and further from solar mid-day and you'll have less energy hitting the panel. Altitude also will affect output, top of a mountain will provide higher output than sealevel (at same latitude, time of day, weather etc).
So, lots of variables and one person in one area of the planet will observe quite a difference in their measured output versus another.
A 100W panel should produce 100W under 1 solar 'unit' (nominal 1000W per square metre at sea level), what it produces in real life will depend on the above stated variables.