Found an URL of .jsp website with GET parameter probably where input is encoded like base64

Can anyone please explain this.

Found an URL in a .jsp website: https://###.###.##/eu/res/viewExamStudentResults.htm?=nSwa6GoRC%2Bsy5uqnd2iSPcdlMOS8WR%2Fz%2FfbusQGa4tU%3D

URL Decoded with www.urldecoder.io : https://###.###.##/eu/res/viewExamStudentResults.htm?=nSwa6GoRC+sy5uqnd2iSPcdlMOS8WR/z/fbusQGa4tU=

Here seems like a GET request with parameter as nSwa6GoRC+sy5uqnd2iSPcdlMOS8WR/z/fbusQGa4tU=

It's like base64 encoded. But unable to decode it properly. Can anyone help on this.