I would recommend to ask this person what "per inch" mean, it's not uncommong to have people using terms wrong or something they invented.
I would suggest asking yourself this questions and then ask them
- Do you have to sketch and ink or will they provide you a sketch that you only have to clean and ink?
- Are you going to do more than just flat black and white, or they'll ask you to do grayscales, textures and more? (This because there are some people that thinks lineart means doing grayscales too)
- How many panels the gig has? Is there a detailed script to follow?
For example, this is why I get by Line Artist.
You'll be provided this:

Then you'll only have to do this:

If they ask you for this, be it more or less complex then that's not doing lineart only, that's doing grayscale, shades, lighting, composition, and more.