ABRSM Beethoven sonatas

why do they say 35, are there an extra 3 that I haven't heard about? http://shop.abrsm.org/shop/prod/ABRSM-The-35-Piano-Sonatas-Volume-1-up-to-Op-14/2001411

Yes, there are 3 sonatinas, I believe without opus numbers, which are sometimes included with the sonatas.

Yes, I think they are WoO: Werke ohne Opuszahl - Work without Opus number.
Check out this excellent website:
http://www.lvbeethoven.com/Oeuvres/ListWoO.html

Don't forget that the juvenile Op.49 ones are often regarded as 'sonatinas' and Beethoven didn't want them published as part of his oeuvre of Sonatas.

Nevertheless they were.

Cooper says: "The three extra ones are normally omitted as they were very early works written when Beethoven was 12. I feel there is no reason to omit them as they are full scale works."

Cooper's Beethoven piano sonatas are so well laid out that it makes reading through the sonatas some much more easier. The fingering is the best and the comments always helpful.

I absolutely love it. (I couldn't resist the temptation to use it before Christmas. )