This sort of shifting of elements by a pixel is quite common. It’s for this reason that we recommend that images contain only single elements of the GUI. In your example, the label is one element and the field itself is a second element. There is a feature in eggPlant that is designed specifically to deal with this scenario: The hot spot (the little red crosshair) can be moved independently of the capture area. This allows you to capture an image of the field label, but have the mouse action occur in a location relative to the label.
When you are selecting an image to be captured, you can hold down the control key (on Windows) or the command key (on the Mac) and move the hot spot independently of the capture area, either by dragging it or by simply clicking where you want to position it. So in this example, put the capture area around just the field label and then position the hot spot over the field, outside the bounds of the capture area. The hot spot determines where the mouse will actually be positioned when a command using the image is executed, so eggPlant will find the label using the captured image, but click to the left of it, where the hot spot is located.
This also allows you to click in a populated field, regardless of its contents, making it useful for selecting elements like the URL field on a web browser. As you continue scripting with eggPlant, you’ll likely find other scenarios where this relative hot spot technique is useful.