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Douglas Fir Larch Strength

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Is there someone can help to explain the following question?
 
The "fb" for Douglas Fir Larch No. 2 is 1250 psi for single memebr based on WWPA's 1988 Manual  "STANDARD GRADING RULES FOR WESTERN LUMBER".
 
However, the NDS Supplement 1991's Table indicates the "fb" value is only at 875 psi (see page 20).
 
Thanks.
 
J. L.