Glitch?

I made a trade offer that zeros out my available cash. The system tells me that I have insufficient funds. It says that I wil have -0.00 funds on hand.
Why is this negative ?
I am thinking that if the - was gone, the insufficient funds warning would also be gone.

Looks like you have an email to support in your future.

I figured it out.
I had .306 dollars remaining.
It was rounded up to .31 on the trade page.
So if trade was made I would be -.004 dollars.