In masino1967’s themes there are some effects for images. These are filters that change the appearance of the image. The names of the filters are very short in order to fit within the text space of the button in the image styles screen. That is why there are arrows symbolizing the change in the appearance of the images.

Examples
→ Invert	shows an image that will turn negative as the mouse hovers over it
Invert →	on the other hand, will do the opposite thing: starting with the image in negative, on mouseover the image will be shown in positive