test(hex8): state conservative weighted packet exponent bound

tests/unit/elements/hex8_high_low_test.cpp

@@ -243,7 +243,7 @@ TEST(Hex8HighLow, UniformDyadicPacketsExerciseEachLowZeroShape) {
           const bool left_low = (shape & 1) != 0;
           const bool right_low = (shape & 2) != 0;
           // Every lane has the same normalized nonzero dyadic inputs. Component
-          // LBE sums are >= -116 and all Add intermediates are bounded by 4.
+          // LBE sums stay above -200 and all Add intermediates are bounded by 4.
           // Thus each Multiply low-shape is uniform and its component products
           // bypass zero/unsupported-tail fallback. No mixed-zero Add fallback
           // is possible; the initial zero accumulator is uniform across lanes.