Filters are affecting each other in the order they are specified! If the original image has the size
60x40and the thumbor url would look like:
then the image will first checked if it fits into
100x100(which it does), then gets the watermark, then it will be blurred (including the watermark), then filled with red so that it will use the
100x100size and at the end upscaled will be applied without having any effect because fill was changing the size of the image already to the maximum available space.