Pretty much what lucounu said, but one thing did stand out as odd to me on the #s you have. My dd14 took the WJ-III at 7.4 so the comparison should be pretty equal. She had grade equivalents of 18 in quite a couple of the "broad reading" tests yet her overall score in that section was well below the 148 you were given for broad reading. If I recall correctly, there were no areas on broad reading where she was below grade 8 equivalency and more of them were in the 14-18 grade range than the middle school area.
Perhaps the test has changed since then (I do recall a lot more subtests than you've listed here), but I'd expect that a 7 y/o with scores in the upper 140s-190s for the composite reading and math parts to have much higher grade equivalencies. Maybe I'm wrong, though.
