Yep .. agree with the others on the cook time.
Here is the recipe I use and I always have great success with it.
1/4 cup butter
1/2 cup brown sugar
1/2 cup white sugar
1/2 cup light corn syrup
1/2 cup sweetened condensed milk.
finishing salt or sea salt
Combine all the ingredients in saucepan
Bring to a boil on medium high.
Cook 6 minutes on med. high heat, stirring every minute.
Temp on the candy thermometer should read about 236.
Pour into lightly buttered glass baking dish.
Sprinkle with your finishing salt or sea salt.
Cut, wrap pieces in waxed paper and store in air tight container.
These caramels will come out rather stiff.
I prefer softer caramels so I double the recipe (no waste on the condensed milk this way!) but still cook the same. Because the batch is doubled but the cook time is not, they come out softer.
Also ... I put my silpat into the baking dish. The candy won't stick to the silpat and it's much easier than trying to get it to come out on it's own.
If your candy is a bit too soft you can store it in the fridge.
I have browned the butter and it gives the caramels a really nice rich flavor.