Hi Laura,
In CMC you can run a security trace. I forgot the exact name of this trace but you will find this in CMC for sure.You will have to run this trace for each folder, to know what level of access does your group "Webi Users" has in its respective folder.
There is no faster way of doing this, thats why its always recommended not to assign "SAP" delivered user groups or access levels in BOBJ. As its difficult to find what level of access they contain.
Also refer to the SAP BOBJ Security guides, you might get some details of the "Webi Users" group.
Note: I have assumed that "Webi Users" is the SAP delivered user group.