Can you please give an example of Grice's maxim of quantity?

Grice's maxim of quantity requires that you make your contribution to the conversation as informative as is needed for the current exchange. For example, let's say that A asks B "What did you have for breakfast this morning?" If B responds, "I had some toast and jam," B is obeying the maxim of quantity, by giving as much information as is needed. However, let's say B responds "I had some breakfast before yoga class. The daily stretching is really making a difference to my fitness!" This is a violation of Grice's maxim of quantity because A) it does not give the requested information about breakfast, and B) it gives more information than is necessary for the current exchange.