As mentioned above the number of lines is not a direct way how to know how long you will read it.
What I do is that I have stop watch (online) and simply start reading (trying to read in my normal speed) it and measure the time it takes me.
I try to adjust the epidodes to approx 15 minutes of my reading speed.
How ever it varies sometimes between 13-18minutes because I want specific ending of the chapter.
In general its recomend to have it minimaly 10 minutes. Shorter usuall piss of the reader . Which is understandable. Tay do not want to spend valuable passes on too short episodes.