Hi Lynnpipe,
You have almost certainly seen/heard a video of a Pommie-crew in action, as they are known to engage in the kind of verbal diarrhea you have just witnessed
. To understand what you have heard it is useful to break up the statement as follows;
First bit "Plus 5 (or Plus 10)": refers to speed above Vref, so if computed Vref is 132KIAS, the speed observed and called by PNF would be 137 (or 142) knots.
The second bit - the "6" that you quote in the middle of every callout, must be the way this particular PNF announces the word "SINK", ie Instantaneous Vertical Speed (IVS) at the moment of the callout.
You have probably therefore already figured out the third part of the
statement - that is the IVS in hundreds of feet, so that for instance "Plus 5 -sink 7" would mean; Observed speed is Vref plus five knots - sink rate is seven hundred feet per minute.
I am pretty sure I know which operator you have heard in action as well, and if I am right -they adopted this whole SOP from a previous BAC 1-11 operation. Their SOP is for the PNF to initiate this whole procedure at five hundred feet above touchdown, and keep blabbering on until the aircraft has touched down.
IMHO - not a very good idea if you are waiting for a late landing clearance, but of course has some merit if the PF happens to be in his senior years (having retired from BA and are now enjoying making noise with a pair of JT8D's) and at five hundred feet AGL have just flicked his reading glasses (that he needs to read the instruments) up to his temples, and can now focus his entire attention at averting the grassy bits surrounding the tarmac bits.
It is however not standard Boeing SOP (and thank goodness for that)
.
Hope this helps - waav8r