Thank you for using PhotoMarks.
This happens because not all of your photos in the batch are of the same size in pixels (or mega-pixels).
Actually the logo/text is of the same size in pixels for all the photos but when the photos are scaled to be displayed on your computer screen the larger ones will appear to have a smaller logo/text.
You can solve this in two ways:
- Group your photos into batches with photos of same size in pixels
- Add the Resize filter with a fixed size before the Date or Watermark filters