I hope you can read since it doesn't say ~10% , it says more than 10% (or >10%). More than means it can be 11% but it can be 30% too.
I think we have someone here who never prepared a ppt to a customer or to senior management. If you have 30% increase on your product performance, why would you write >10%? That's right, you don't. It's outright stupid. If you have 30% on the sleeve what you do now is to generate a lot of hype to the product without disclosing your secret sauce. Promise and deliver 30% puts you in a very nice spot. In business language, and you can bet your paycheck that AMD senior management reviewed what the guy can or cannot talk, >10% means 10%, 11%, 12%, maybe 13%. If you can reach 14% you'll write ~15%, not >10%. It never means 30%. Never.
Looking back at x86 history, I can't recall any other time beyond Netburst => Conroe when we had >30% increases on IPC, and even then clocks were down by 40%. IPC increases of the same arch usually sits between 5% and 10%, so if they get 10% with only adding 10% on xtor budget, a near perfect scaling, that would be quite a feat already.
As for the clocks, going from 2 to 4 cores puts a great burden on the thermal budget, so doubling core counting and still being able to rise frequencies isn't something trivial. The first slide stating 10% doesn't seems too out of touch with reality. The assumption here is that a 28nm bobcat core with double the number of cores would have roughly the same frequencies.
That's what you do to obscure the information about the product that's not yet launched(and to protect it due to competitive reasons).
I surely wouldn't want everyone knowing totally the merits and flaws of my products, as it would give my competitors an unneeded head start to counter my product, but a rough but accurate performance estimate without disclosing what I did to get there generates the kind of good hype for the product that brings OEMs in, that makes key people and companies interested in knowing what I have, and even better, some very good news to announce to investors at the EC. It is the "how" that cannot be disclosed.