Google says it is 216 x 152 x 45 cm. Next time you have your awning up or perhaps you can lay it out, measure up the space size. Alternative google your awning annex model, you should be able to get the dimensions.
I thought this had been covered fairly recently. The majority of Kampa/Dometic air awning annexes are showing in the brochure as 200 x 180cm. The taller awnings are possibly 220 x 180cm.
Alex2x