Yeah, according to ISO, it should be without the plus sign.
I have yet to figure out how to do this in Creo without overwriting the dim text. I usually just make it show as 71+1. So, in this case I would just put +1 into the sufix of the dim text, which is also fine according to ISO.
Maybe I don't understand what you mean by "parametric method". It appears you manually entered the tolerance in which case you can simply delete the "+" for the lower tolerance.
If the tolerance was parametric, the dimension would only show as "@D".
So it might be that you need to go into the model and re-format the dimension if in fact it is formatted in the model.
