There is no ink in my stomach.

Next sentence: it is difficult to spend long in a pen.

Metaphor is a low level of education, no knowledge, and writing with ink. The ink in my stomach describes how much knowledge I have, but there is no ink in my stomach. There are two meanings, one is modesty, which means that I have little knowledge, and the other is that I have no education, low cultural level, little knowledge and limited knowledge. There is no deep analysis and understanding of things, and the level is limited.