The ranking is a measure of research relevance across higher institutions of learning across the globe.
Four web indicators are used to determine the academic value of research conducted by institutions across the globe. E.g the excellence indicator measures the top institutions in the world with the highest citations/references from researchers/lecturers/scientist for the past four years. Currently, University of Capetown and Stellenbosch university has the best citations so far in Africa. It is important to note that Webometrics differs from Times Higher education ranking which employs a more wholistic approach at the ranking by using teaching, research, industry and international outlook.
Lalasticlala Myndd44
Released 2, February 2017
Webometrics.info/en/Africa

There is a lot of misconception about the purpose of webometrics rankings. Some say it is to measure traffic to university website which is very WRONG.
Webometrics uses four main indicators but let me explain just one. For instance if a Unilag lecturer writes a scientific journal on Elsevier and puts it online and another lecturer from Stanford university cites or uses that Unilag publication for his own scientific report. That Unilag journal would immediately receive a point that would accrue to the lecturer and the university online profile(this is called excellence indicator). At the end of the year the Cybermetric lab in Spain then extracts all the citations from all universities and rank them
Lalasticlala Myndd44