@oristarA,
In music parlance, to "top the chart" means to sell the most records over a period of time (usually a week). It therefore denotes the most popular music recording at that time.
For instance, The Beatles "topped the charts" many, many times.
It therefore illustrates popularity or amount of usage, etc.
Nowadays it could also mean the amount of "hits" something receives on the internet, to which I think your piece is alluding.