Because it's a nonsensically small number; and it's contradicted with the graph immediately below it, that shows larger amounts of energy (MWh) generated in individual hours, than the supposed figure for the entire week. The peaks on the graph are ~40,000 MWh/hour sustained over multiple hours (eyeballing it). The amount generated in the entire week can't be 17,000 MWh, a number smaller than that.

(For anyone unclear about units: the y-axis of the graph is GWh/h, the same as 10^3 MWh/h, or simply just 10^3 MW. The unit [MWh] = 10^6 [Watt]*[hour]).

Yes, the units are correct. But currently Germany is generating 33 GW of solar power (according to electricity maps). Therefore the 17GWh is generated after 0.5 hrs. For a whole week this value is way too low, even if it was a cloudy week (which it wasn't).