I know that in PRT you can choose wich of the two options you want in “Trading options”, careful because in my case the “keep the two positions” was set by default (so wrong in my opinion!), so I had a unpleasent surprise the first time I trade in PRT. But if you open the position in IG plataform and later you open a opposite position in PRT I am not sure, my guess is that PRT don´t know about the first position so it will open another position. If you really want to know just try 🙂