What do these timber codes mean?

[JP_]

Using some 2x4s from demolished flat garage roof to replace rotten floor joists. Going to treat everything anyway, but what does all this mran?

 

[John D v2.0]

Only one i get is C16 strength grade!
PEFC is prospective earth fault current

 

[Ian H]

The other number mean that it's best before date is the 32nd May 2020

 

[JP_]

Lol, thanks. Well, it's wood, so it'll do!

 

[Notch7]

Only one i get is C16 strength grade!
PEFC is prospective earth fault current

Programme for the Endorsement of Forestry Certification.

IS444 strength: use of structural timber in buildings (superceded by C16)

Sodra: Swedish timber company.