In U.S. English, we read from top to bottom, left to right.
‘Best Selling’ may not mean the number of reviews a gig has received - perhaps the $ value of sales? I suppose it depends how Fiverr has decided to implement it?
Though online dictionaries say “best selling” means selling in “large quantities” (or similar) not for the most amount of money. So surely for the most accurate display they should show gigs that have sold the most in quantity, not based on price. Maybe it also takes into account (or should do) the last x number of days eg. the gigs that have sold the most (in quantity) in the last 30/60/90 days.