Cleaner for liner above the water line

[Manon]

I have been given a product called Net'bord Gel to clean the slightly dirty liner above the water line in our pool. The instructions seem rather confusing / contradictory but I think you just sponge it on, leave for 5-10 minutes and then wash it off using a soft brush or cloth and rinse with the pool water. Is this correct - has anyone else used it ? Very grateful for any re-assurance !