dovecot - Jan 2020 - sieve size match with multiple of 4GB not matching (BUG?)

Hi,

I have noticed a strange behaviour when using size matches with GB in
sieve.
If I use filter that matches mails smaller then 4, or 8GB it does not
match in any case. 
same filter matches with 3,5,6,7 GB 

example filter:

require "vnd.dovecot.debug";
if allof (size :under 4G)
{
        debug_log "MATCH";
}
else
{
        debug_log "NO MATCH";

}

# sieve-filter -u johnd filter.sieve INBOX
>> Filtering message:
  ID:      <5167DFC8.8040207 at XXXXXX>
  Date:    Fri, 12 Apr 2013 12:19:52 +0200
  Size:    1820898 bytes
  Subject: Fwd: Multi-media mail demonstration
info: DEBUG: NO MATCH.

**************************************************************************


same mail with this sieve rule:

if allof (size :under 5G)
{
        debug_log "MATCH";
}
else
{
        debug_log "NO MATCH";

}


# sieve-filter -u johnd filter.sieve INBOX
>> Filtering message:
  ID:      <5167DFC8.8040207 at XXXXXX>
  Date:    Fri, 12 Apr 2013 12:19:52 +0200
  Size:    1820898 bytes
  Subject: Fwd: Multi-media mail demonstration
info: DEBUG: MATCH.



same for M. 
4096M => NO MATCH
4097M => MATCH


Greetz Matze