The consensus seems to be one turn.  The string has to be turned in
the right direction.  Counter-clockwise is usually it but never assume
-- check it.  Look closely at the copper coil wrapped around one of the
larger bass strings.  Right where the winding ends, the end of the coil
will be pointing in the direction it should be turned.

I've seen some foreign manufactured pianos that wind the upper bass in
a different direction than the lower bass.  I know the winding is small
and hard to see, but check the upper bass also.  I've seen defective new
strings that continue to buzz after being turned; I just order a new
string if that's the case.

Bill  Maguire