idiom question

Duff: a boiled or steamed pudding often containing dried fruit
(webster dictionary)

直譯這句就是食布甸時, 淨係挑晒D乾梅食, 唔食D麵粉呀蛋呀的
布甸料.
即是說唔照單全收, 要呢D唔要果D, 淨D正先要.

pick the plums and ignore the duff
not sure about this... but i think it means that you cannot just take into account the things that pleases you and not consider the things that doesn't