Tinydns failover ping

[tempus6]

I almost have roundrobin failover DNS working for my domian.  documentation is scarce and I dont fully understand the following parameters in tinydns:

On the add/edit record page:

• ping threshold
• WAN ping threshold

And on the settings page:

• Refresh Interval (what time unit is this in, and is this parameter global for all failover ip's in tinydns?)

Anyone have a clue what exactly these do?