I am not an expert on the science behind these toolboxes, you will need to wait and see if someone in the community can help.
In the meantime perhaps you can ask the question in the Atmospheric Toolbox dedicated forum.?
Also Falah posted a very nice tutorial (on the use of Atmospheric Toolbox) on this other topic, perhaps this can help you.
I can also suggest that you try to pose your question clearly! Why do you need to open the S5P Products in SNAP? Are you trying do use them together with other data? Please explain the use-case so that people can understand it and provide adequate feedback.