Sounds about right. The default Target SNRm for ECI's is 6.3dB.
As others have said would also need to see more stats, but I'd guess with you being 6.4dB that your line conditions have slightly improved since you last sync'd.
Most lines SNRM will vary over the course of the day. 0.1 dB is going to make very little difference to your attainable speed.
As regards to the upstream, usually that indicates a line that has full 20Mbps/10Mbps upstream sync (depending upon which product they are on).
For example these are mine
Max: Upstream rate = 25642 Kbps, Downstream rate = 67508 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 67469 Kbps
SNR margin (dB): 6.3 9.1
The 9.1dB shows that I have surplus SNRm whereby if the upstream rate wasn't capped at 20Mbps, then my line would be capable of attaining 25.6 Mbps upstream.