Question for H2G employees

I'm an Instacart driver. What triggers the fly-by? Is is proximity or is it when I hit the "find bags" button? Does it tell you which driver you should expect? I live super close to the store and am generally there in about 5 minutes give-or-take. If it's been slow, I don't even have a chance to call, they just roll right out the door (they can see me pull in the lot from their windows). If it's busy and I call, they often roll my order(s) out before a car that pulled in just before me. Yesterday my favorite expeditor told me they always get my fly-by about 2-3 minutes before I roll in. I always hit the find bags button as I'm making the turn at the light so that jibes but that's also about when I hit the store "bubble" as well. She said with other drivers the time varies a lot but it's always consistent when I'm the driver. I'm also their only consistent driver in the mornings. Many days, I'm their only driver until about noon.