Solar panel ratings are often misleading and at the very least confusing.
Without a load on the panel, it will read a particular voltage - called the 'open circuit' voltage. Kind of like the voltage you read on a battery that's not connected to anything. Once you put a load on it, the voltage drops - the greater the load, the greater the drop until you reach the maximum current output of the panel.
Maximum current output is NOT achieved at maximum voltage (because max voltage is when there is NO load at all). However, manufacturers rate their panels in watts and a glib salesman will even pull out Ohms Law to show you that Power (watts) = I (amps) times V (volts). This is absolutely correct, but there are 4 different ways to get the result.
The honest way: the amps produced under peak load (sometimes referred to as the Max Power Current) times the voltage under peak load (Max Power Voltage) = panel watts. One of the panels I looked up on eBay had the peak volts at 17.82V and peak current at 8.9A, which results in 159.598Watts - close enough to the claimed 160W.
What they COULD have done was use the open-circuit voltage times the short-circuit current, in this panel's case that was 10.68A times 21.96V = 234.53Watts.
That's outrageously high, but there's nothing stopping an unscrupulous trader from taking the short-circuit current times the open-circuit voltage on an 80W panel (from another example on eBay, 5.1A times 22.5V = 114.75W and try off-loading it as a 100-120W panel. You'd believe it until you tried using it and only got the 4.45A that an 80W panel is capable of.