There are many ways to know when your garlic is ready.
Most of us like to look at the lower leaves, and I did it that way for years.
When the lower leaves begin to brown and die back, by the time you have 2, 3, or maybe even 4 leaves brown it is time.
But I found that the Garlic scape will also give you an indicator when it stands straight up and begins to open.

Hope you are having a great day.

May you be Richly Blessed.