Sort of misleading. I wouldn't compart `notfound_ok` to "setting R to 1". How about just shortening this sentence to the relevant parts, and fixing some language (eg. `not_found` isn't an error, per se).

"If `notfound_ok` is set to `true` (the default value) and the first vnode to respond doesn't have a copy of the object, Riak will assume the missing value is authoritative and immediately return a `not found` result to the client."