In this page of ImageGrab Options you can change some elements of the behavior of the application. If you hover over an item on this panel, then an explanation is displayed.
Reset the numbers to 1 when you open a video: When you number images captured with ImageGrab, they increment each time you capture. If you open a new file, this numbering can reset to 1, or continue there it was.
Save the image when click on the video: When we click on the video, the image is captured on the clipboard. It can be saved simultaneously – according to the settings defined in the Image saving Panel – if you check this box.
Confirm before replacing an existing image: Check this box to prevent ImageGrab from overwriting an existing image that had the same name. When you save an image, you will be asked for confirmation.
Note that you can answer Yes to All, which will have the effect of unchecking this box and not asking you for confirmation until further notice.