As Vincent says. W=(Watt) is NOT the same as Wh (Watt/hour).
You´r Fibraro do the calculation for you,
When Fibraro shows Wh, it shows the generated Energy the light has consumed, calculated in hours.
When Fibraro shows Watt, is shows you the actual power consuming when the light is ON.
If you want to calculate yourself, then you need to understand the difference between W and Wh. And then you have to calculate from what Vincent says.
One 10Watt bulb set to ON (max dimming assumed) in one hour, will have consumed 10Wh Energy.
In two hours, it will have generated 20Wh of Energy.
In practice, (assuming your Fibraro has been reset til zero):
When you turn ON the above 10Watt bulb, Fibraro will show 10W consuming in real time.
After one hour with light set to ON, Fibraro will show 10Wh as well, as this is the power consumed in one hour. Also called Energy. (Fibraro shows this data in real time as well, because it do the calculation for you).
Totalt energy consuming Wh will be the sum of all time the light has been set to ON. This is the energy you will be charged for as well, from you power/grid supplier. (electric company).
A 500Watt “thing” turned ON for 10 minutes, will have consumed 500/6 = 83.33Wh Energy after one hour.
If you turn it ON twice within the same hour, or leave it ON for 20 minutes, it would be 500/3 = 166.66Wh Energy in an hour.
This calculation can be done for normal restistance (Ohm) things. Don´t know the exact word in english. But a few things is a bit more complex to calculate, ie transformers, 2/3-phase motors, electric heaters etc. To calculate those, you´ll have to include cos/fi as well, (as far as I remember), which makes it rather complex. But most stuff in a normal household can be calculated direct from the above.