The counter is incremented by 1 when processing an A4 page or smaller.
When processing a page which is n times larger than A4, the counter will be incremented by n.
So, most probably the size of the image you are processing is too large (compared to A4). Open the image in an image editor and check if the image dimensions are larger than the A4 page dimensions (210 mm x 297 mm, or 8.3 in x 11.7 in).