The delay on the grandsteam DP750 phone is exactly 10 seconds, why?

Question

Asterisk

I welcome everyone.
It costs Elastix on it to set up IVR without any special features, after losing the acapella, a call to the administrator should go immediately, it goes but comes with a delay after a voice greeting of exactly 10 seconds. I can't understand why, in Elastix everything is set to 0 in terms of waiting for user action. I can’t figure out where to dig, the phones are controlled by GRANDSTREAM DP 750. I haven’t seen this before. Here is the IVR plan