Editorial: Insert the mathematical value of

The phrase "the Number value for X" is only defined on mathematical values,
but `_prim_` is a BigInt value here.
So we have to take the mathematical value of `_prim_`
before applying "the Number value for ..."

spec.html

@@ -26572,7 +26572,7 @@ <h1>Number ( _value_ )</h1>
         <emu-alg>
           1. If _value_ is present, then
             1. Let _prim_ be ? ToNumeric(_value_).
-            1. If Type(_prim_) is BigInt, let _n_ be the Number value for _prim_.
+            1. If Type(_prim_) is BigInt, let _n_ be the Number value for the mathematical value of _prim_.
             1. Otherwise, let _n_ be _prim_.
           1. Else,
             1. Let _n_ be *+0*.