Wierd md5 error with bytes

I have a rare error (or at least I think it is) with md5. Namely, I understand that md5 gives out a result of 128 bytes, 128 / 8 = 16 bytes. This is the same as with CC_MD5_DIGEST_LENGTH from CommonCrypto. However, if I use Insecure.MD5 from CryptoKit, the digest has 20 bytes with zeros at the end… Is this intended or is it really an error?