The normal way would be to have your Blynk button widget attached to a virtual pin, and when it’s pressed it triggers the BLYNK_WRITE(vPin) callback function.
With this approach, no ‘polling’ of a digital pin is required.
If you also have a physical button attached to the device then you should probably be using interrupts and a debounce routine, or you could poll the switch using a timer.
The code in this topic uses the polling option for the physical button, and to be honest 10ms is a bit of an overkill.
Pete.