I really don't know how they are calculated, but I have to think there is something off in the scoring on the reading. My DS was given WJ Achievement just before he turned 7. His scores were as follows

147 Broad Math
145 Calc
140 Applied Problems
109 Fluency

133 Broad Reading
141 LW ID
131 Pass. Comp
117 Fluency

His scores compared to your DS makes me think maybe there is a typo somewhere but I don't know?