Liquify Brush Size Too Small

I'm working on a canvas that is 540 x 1080 and using the Warp brush in Liquify Tool for an effect, but for some reason, the brush remains rather small despite pushing the size to 600px.

Here's my settings:

And here's how the brush size looks.

I've been watching other AE tutorials using this effect, and whenever they scale the brush up to 600 it takes up the size of nearly the entire work area. No matter how many times I apply this effect, it never gets larger than what you see above.

I'm still new to AE, so if there's a really obvious thing I'm missing please let me know. Thanks.