Hydrometer accuracy with warm sap?

[adironmaple]

On monday the temp got up to 75. Even with collecting several times per day at all 3 bushes the sap was warm. When I tested for sugar the weighed average for over 10,000 gallons was 1.47. We processed all sap that evening and ended up with 210 gallons of syrup. If my math is correct thats way more syrup than this lot of sap should yield. Same thing happened yesterday but to a lesser extent cause it was not as hot.
Started thinking my hydrometer was bad so I took a new one out and read exact same as old one.
Printed on the hydrometer is that it is for sap at 38 degrees. So my question is how do you calculate the sap content based on sap temp? Is there a formula or publication available that I can use.
We buy a little sap and plan to buy alot more in the coming years so want to get it right for everyone involved.

[saphound]

I don't remember where I found this, but I copied it into a notepad file for future reference..
For a 38 degree calibrated sap hydrometer
32-46 degrees add .0 brix
47-56 degrees add .1 brix
57-61 degrees add .2 brix
62-64 degrees add .3 brix
65-68 degrees add .4 brix
69-72 degrees add .5 brix
73-75 degrees add.6 brix

Did you ever take a temp reading of the sap?
A way to double check this chart would be to cool a sample to at least 46 degrees and test it again.
Also, it seems if you know how much sap you boiled and how much syrup it made, you should be able to do reverse math with the rule of 86 to get sugar content. Of course, that won't help when you're buying sap. Just a way to get an idea of where the sap really was that you just processed.

Edit: I believe this is where I copied it from:
http://andersonsmaplesyrup.com/files/HydrometerTempCorrectionChart.pdf