diff --git a/u_tls_extensions.go b/u_tls_extensions.go
index a76637e..2eccfba 100644
--- a/u_tls_extensions.go
+++ b/u_tls_extensions.go
@@ -854,9 +854,9 @@ func (e *ApplicationSettingsExtension) writeToUConn(uc *UConn) error {
 }
 
 func (e *ApplicationSettingsExtension) Len() int {
-	result := 7
+	result := 6 //id + first length + second length
 	for _, element := range e.SupportedALPNList {
-		result += len(element)
+		result += 1 + len(element) //byte for string length + allocation for string in bytes
 	}
 	return result
 }
@@ -868,22 +868,21 @@ func (e *ApplicationSettingsExtension) Read(b []byte) (int, error) {
 
 	b[0] = byte(extensionApplicationSettings >> 8)
 	b[1] = byte(0x69)
-	b[2] = 0
-	b[4] = 0
-
 	currentIndex := 6
 
 	for _, alpn := range e.SupportedALPNList {
-		b[currentIndex] = byte(len(alpn))
+		b[currentIndex] = byte(len(alpn)) //set length of string in bytes
 		currentIndex++
 		for _, char := range alpn {
-			b[currentIndex] = byte(char)
+			b[currentIndex] = byte(char) //convert char to byte
 			currentIndex++
 		}
 	}
 
-	b[3] = byte(currentIndex - 4)
-	b[5] = byte(currentIndex - 6)
+	b[2] = 0x00
+	b[3] = byte(e.Len() - 4) //len minus id and itself (2+2)
+	b[4] = 0x00
+	b[5] = byte(e.Len() - 6) //len minus id big length and itself 5 (2+2+2)
 
 	return e.Len(), io.EOF
 }