I am not sure that I understand the problem. As far as I see you're accessing the series correctly.

Only if you want to use the same series in a TMF, you need a global variable. The difference between global and local variables is explained in the "Variables" chapter. Declare the vars outside the function:

vars Dot11High;

and set it in your run function:

Dot11High = series((Close[0]+High[0]+Low[0])/3*2-Low[0]);

Then you can access it also in a TMF.

If you get wrong values, print them all together in the log - you can then see which value is other than you expect.