fixed wrong coordinate

htab.h

@@ -11,7 +11,7 @@ typedef struct {
 } ha_mz1_t;
 
 typedef struct {
-	uint64_t rid:28, pos:27, rev:1, span:8;
+	uint64_t rid:28, pos:27, rev:1, span:8; // actually it is not necessary to keep span in the index
 } ha_idxpos_t;
 
 typedef struct { uint32_t n, m; ha_mz1_t *a; } ha_mz1_v;