Can't adjust a large size in AI

That's right. Illustrator can't do that. As the popup box in your screenshot tells you, 227.54" is the maximum width and height in Illustrator.

Now comes the inevitable question; Why? Why is that the maximum? Why is there any maximum at all?

The plain fact is; there is no good reason. I can name any number of other vector programs with no such limit. And it has been presented to Adobe again and again as a feature request for at least the last eight years that I know of personally. It is just one of a number of annoying deficiencies in this "industry standard" software that have never been addressed, despite years worth of requests and pleas by the people who use their software every day. A failing that seems to be increasing with this new 'Cloud' scheme.

In short; you will have to work in scale (manually divide everything by two, or four, that is; Illustrator not having and actual Scale function -- another of those deficiencies), or switch to something like Corel.

Just another frustrated user.

--OB

BTW: The actual Illustrator forum is HERE. You'll get quicker answers if you post your questions there.