chore: tidy comment and code of CpcSketch

Signed-off-by: tison <wander4096@gmail.com>

Author: tisonkun

src/main/java/org/apache/datasketches/cpc/CpcSketch.java

@@ -621,7 +621,7 @@ private static void updateWindowed(final CpcSketch sketch, final int rowCol) {
     assert ((sketch.windowOffset >= 0) && (sketch.windowOffset <= 56));
     final int k = 1 << sketch.lgK;
     final long c32pre = sketch.numCoupons << 5;
-    assert c32pre >= (3L * k); // C < 3K/32, in other words flavor >= HYBRID
+    assert c32pre >= (3L * k); // C >= 3K/32, in other words flavor >= HYBRID
     final long c8pre = sketch.numCoupons << 3;
     final int w8pre = sketch.windowOffset << 3;
     assert c8pre < ((27L + w8pre) * k); // C < (K * 27/8) + (K * windowOffset)

src/main/java/org/apache/datasketches/cpc/CpcUnion.java

@@ -124,7 +124,7 @@ public CpcUnion(final int lgK, final long seed) {
     bitMatrix = null;
     // We begin with the accumulator holding an EMPTY_MERGED sketch object.
     // As an optimization the accumulator could start as NULL, but that would require changes elsewhere.
-    accumulator = new CpcSketch(lgK);
+    accumulator = new CpcSketch(lgK, seed);
   }
 
   /**