(Lead Editor Saji's response came while I was typing the content)
Editors evaluate the contents posted in various sections and assign cash credits as per their judgement. Since quality factor is to be evaluated, there cannot be any pre-disclosed parameters as quality cannot be quantified. There are certain type of contents e.g. for posting a question in the 'ask expert' section, cash credits are not assigned though in respect of posting quality answers, cash credits are awarded. As far as forum section is concerned, cash credits are assigned by the editors in respect of outstanding contents - be it a forum thread or a thread response.
Maximum cash credits in one go can be earned by posting quality articles. I have earned maximum 90 cash credits in respect of one of my articles so far. But there are cases where even more cash credits were assigned in respect of articles of exceptional quality.
Let us encourage each other in sharing knowledge.