Pretty hard to answer without knowing more details.
Could this be possible to achieve? Yes. For example if you have a website that isn’t doing well an only gets 100 hits a month then yes you could increase it by 1000% with the right changes and targeting.
Do they explain why it would increase by a 1000% by making the changes?
When reading the suggestions does it make sense and actually seem like a good idea?
And lastly…it doesn’t really matter if it’s 1000% increase or 100% increase. Any increase is good, as long as the changes you are making don’t cause a decrease in any way.