I suspect something else is going on. As a test, I constructed my own array and sent the data out to an LCD using the STR variable\6 command. Worked either way I constructed the equation.

ab_Test[0] = "0" + Heading DIG 2
ab_Test[1] = "0" + Heading DIG 1
ab_Test[2] = "0" + Heading DIG 0
ab_Test[3] = Heading DIG 2 + "0"
ab_Test[4] = Heading DIG 1 + "0"
ab_Test[5] = Heading DIG 0 + "0"