Actually, without specifying an index, it should default to the sum. So:
-gltsym 'SYM: +Ant.Mean -Ant.Nice' -glt_label 3 Ant.Mean.V.Nice
would be (assuming just 1 AM param) the same as:
-gltsym 'SYM: +Ant.Mean[0] +Ant.Mean[1] -Ant.Nice[0] -Ant.Nice[1]' -glt_label 3 Ant.Mean.V.Nice
And you presumably do not want [0] added in.
- rick