What kind of pay increase should I be looking for when I’m asked to train/supervise another coworker?

Right now I’m the only graphic designer at a company with less than 100 employees. After talking to some of the higher ups a couple times, I got them to consider hiring another person to help with everything. The company has been growing so I’ve been getting slammed with work over the last few months.

It looks like we’re going to be hiring from within from a different department and the person is someone I get along with so I’m thinking the training will go smoothly. Anyway, the last time I brought it up they said that I would be getting a pay increase since I’d be training and supervising the new designer and they have pretty limited experience in this field.

We’re having another meeting about it in a couple weeks so I was just wondering if there’s any type of number that I should be looking for in regards to having to train and supervise someone?

Not sure if it matters but this is my first job out of college, I’m making $40K now, and I’ve been working at this company for about 2 years.