I looked at the "all" timeline graph for France here [1]. Could someone explain why the big jump ~2012 ?

[1] https://agsi.gie.eu/data-overview/graphs/FR

The "added" capacity is close to Storengy's total capacity.

My guess is that the chart is missing pre-2012 data on those sites.

Germany: stored 239.64, consumption per year 905.30 ⇒ 239×12/903 ≃ 3.17 months

Spain: stored 32.99, consumption per year 338.99 ⇒ 32×12/338 ≃ 1.17 months

However, the “Stock/Cons” column, annotated with “Filling level compared to annual consumption”, shows this:

Germany: 26.47 ⇒ 26.47×12 ≃ 317.64 months

Spain: 9.73 ⇒ 9.73×12 ≃ 116.76 months

What did I misunderstand?

Stock/Cons is in percent, if you divide your 317 months by 100 you get the expected result.

Ah, thanks! I thought it was a ratio. I should have noticed the % symbol in the column header.

Does anyone know what the consumption number refers to? Daily? Weekly? Yearly?

Yearly. See the tooltips in table headers.

Annual consumption, it declares so when you hover over it.