Total time is how long the modem had been powered on.
Since link time is since the xDSL link was established.
That's the weird thing. The modem was rebooted 5 days ago, so the sync time and total time should be within a minute or so of each other.
In fact from the DSLstats UI at this specific moment in time I see:
Modem uptime: 5 days 21 hours 28 min 36 sec
Total time: 1 days 21 hours 28 min 30 sec
Since Link time: 5 days 21 hours 28 min 3 sec
Total time is sometimes missing a digit on some (I can't remember which) devices.
It may show 1 day instead of 11 days.
In this case it seems Total time always reports 0 or 1 for the day value, never going higher than 1.
Modem is running as follows (this taken a few mins after the above):
Product type EchoLife HG612
Device ID F4559C-21530315408K1B094465
Hardware version VER.B
Software version V100R001C01B030SP08
Firmware version A2pv6C038m.d24j
Batch number BC1P6.030.A2pv6C038m.d24j
System up time 5 days 21 hours 32 minutes 54 seconds