I'm certainly not a VA expert, but...
You will have to front the cost of your training, and VA will reimburse up to 60%.
The "cap" is the total amount available to you under the GI Bill (i.e., 36 full-time academic months at the current payout rate---which is just over $1k per month right now).
Additionally, all of this is conditional on your going to a Part 141- AND VA-approved school.
And FWIW, here's something I've been toying with... (1) use your GI Bill towards a degree at a relatively inexpensive state school, (2) bank all the funds the Bill pays beyond your actual expenses (iow, don't spend a dime of it on anything but actual school expenses), and (3) use those saved up dollars as far as they'll go at a good Part 61 school.
Good luck.