Apparently I cannot subtract two points without getting NaN instead of 1.0:

```
var lastGallon = gallons.lastValue(1);
var dt = gallons.time - lastGallon.time; // time between last gallons (ms)
return dt; // Success. result=176000.0
var dg = gallons.value - lastGallon.value; // number of gallons
return dg; // Success. result=NaN
return gallons.value; // Success. result=422536.0
return lastGallon.value; // Success. result=422535.0
return 422530.0 - lastGallon.value; // Success. result=NaN
return gallons.value - 422535.0; // Success. result=1.0
return gallons.lastValue(1).value; // Success. result=422535.0
```

This seems to have broken during an upgrade or a restart back in November. What is wrong?

Also, I can't find the documentation on using the logging function in metadata scripts. Where is it?

Thanks.