I have taken a look at this page: http://oldweather.s3.amazonaws.com/ow3/final/Commodore%20perry//Volumes/Seagate%20Backup%20Plus%20Drive/Arfon-JPEGS/RG26/COMMODORE%20PERRY//vol176/vol176_073_1.jpg
is that the numbers in parentheses are what the log reads since when the log is put over it reads 7.7 and then the course is ExS until the log reads 9.3, and then the course is ESE until the log is 12.6 and then "4:50, Tree Point Lt. abeam, distant 1 mile (20.4)."
There is no need to transcribe those numbers unless
they are in
something you are transcribing - TWYS
I would transcribe the location as
Location | Place Name = 4:50, Tree Point Lt. abeam, distant 1 mile
Location | Place Name = Tree Point Lt. abeam, distant 1 mile
and not include the log reading.
On the other hand, if the log says "Guard Id. (42.3), distant 0.7 mile", you should include it:
Location | Place Name = Guard Id. (42.3), distant 0.7 mile
Hope this helps