What does AR(max=1) mean? http://cocodataset.org/#detection-eval
"ARmax=1: AR given 1 detection per image"
"AR is the maximum recall given a fixed number of detections per image, averaged over categories and IoUs."

Above link, they described ARmax=1, but I didn't understand exactly. I understood general recall concept in machine learning or other areas. Could you explain ARmax=1 more detail ??
AR is the abbreviation for Average Recall.
max=1 only looks for 1 detection per image.
Thus, ARmax=1 is the average ability of the model to find a given category in an image. For example if there is a dog in the image, the model should predict a dog in the image. That performance is averaged across all categories.