Having older ETS Professional licenses does not entitle you to receive more credits. The credits are given for one professional license per MyKNX partner account. In the above case you will receive credits for the ETS5 Professional (but these will be higher as you have a license of the latest ETS generation).
I bought in the past also ETS3 and/or ETS4 Professional. I now have an ETS5 Professional license in my account. Will I get extra credits?
