Comes from the mahjong game, which means more number of games win, Many little things add up, it also interpreted as "Puerile"
Definitions (粵典–words.hk)
語句
指打麻雀嗰陣連續幾次嘅「和」,抵返上一次三番;即係積小勝為大勝 a lot of small gains is as good as one big gain (e.g. business can prosper by a high volume of sales at a low profit margin); literally: a series of small wins is as good as a big win