diff --git a/mix.go b/mix.go
index 38a4397..86e44cc 100644
--- a/mix.go
+++ b/mix.go
@@ -11,10 +11,10 @@ func fas_mix(sum_nex []dna, sum_charset []charset) (map[string][]string, int, in
 
 	sum_dna := make(map[string][]string)
 
-	for _, v := range sum_nex {
-		for k1 := range v.min {
-			_, has := sum_dna[k1]
-			if !has {
+	for _, v := range sum_nex {  // v is sequence of a sample in a file
+		for k1 := range v.min {  // v.min is sum of intaxname and indsq
+			_, has := sum_dna[k1] // k1 indataxname
+			if !has { // has is true, not have is false
 				sum_dna[k1] = make([]string, len(sum_charset))
 				ntax++
 			}
@@ -24,10 +24,9 @@ func fas_mix(sum_nex []dna, sum_charset []charset) (map[string][]string, int, in
 		for _, v1 := range v.min {
 			for k2 := range sum_dna {
 				if _, ok := v.min[k2]; ok {
-					sum_dna[k2][k] = v1
+					sum_dna[k2][k] = v1 //include is fine
 				} else {
-					sum_dna[k2][k] = strings.Repeat("?", v.count)
-					// 之前就没写错吗？已修复
+					sum_dna[k2][k] = strings.Repeat("?", v.count) //not include, repeat string ?
 				}
 			}
 		}