With the Admonition upgrade is it allowed to discard 4 tokens to cancel 4 dices of the same attack?
Admonition, múltiple token discard at the same attack
No.
The "While" trigger only allows you to do it once for each attack.
What the boss said.
However, it's probably worth pointing out that, as long as a token is readied (green), it is allowed to spend it to provide its usual effect (which exhausts it to its red side) and then immediately discard it to also trigger the Admonition effect.