OK, if this is your requirement, you could do it as outlined in the image shared below:
In the survey tab of your xlsform:
In the choices tab:

Data entry screen as seen in Enketo:
Reference xlsform:
Repeat Group.xlsx (11.6 KB)
OK, if this is your requirement, you could do it as outlined in the image shared below:

Repeat Group.xlsx (11.6 KB)