Scantlings

In Dave Gerr's book the elements of boat strength there is a rule for sawn floors. In my case, it gives the floor molding of 300 mm. What puzzles me, is that measured from the bottom line extensions intersecting at keel, or from above the keel batten? If somebody could clarify me, I'd be grateful.

 

I gather that it is the actual dimension of the floor member.

 

The book gives you all the definitions, including where the measurements are taken from.