How do I change the size in Input Manager?

Hello,

Should be extremely easy right? Apparently not for me -.-

I am a brand new Unity user and I'm following a tutorial to create a basic Pong game using the free version of Unity 5.2.2

After fulfilling the first steps, I am now at a point where it has asked me to increase the size of the Axes from it's base of 18, to 19. The problem I am having is that when I click into the size field, I type in a new size of 19, but as soon as I click out, it automatically reverts to 18 and doesn't add any lines. This isn't happening in any of the other fields under Input Manager and I have followed the tutorial to a T. I'm frustrated that there is no information I can find to explain why the size field is behaving this way. This version of Unity is fairly new so I guess there isn't much specific information or remarks on it yet.

The person who made the Pong tutorial seems to think I need to do it for the next step so I'm trying to. Any help as to why I can't click in the field and just type a new size in and what to do about it would be appreciated.

Thank you so much!