I do not know if the “%” was a typo but that character does nothing to the sprite sheet unless some sort of plug in is used. U/seventhirtysixam provided a decent explanation on where you can go to understand the rules for formatting but I will also drop this link to a formatting guide I used when I first started. The only way this would work is if the cells were the same size (the image inside the cell can be whatever size as long as it fits in the cell). If these arent big enough for you, you can increase their size by full percentages (so 200 or 300 bigger) as long as you keep the pixels sharp (using. In the middle and bottom pics you have sprites both 1 tile and 2 tiles in height (and I think width?) the program can’t read sprites on the same sheet with different heights and widths. These are animated SV Battlers for your heroes to face Based on the default monster images, these should bring a bit more life to your battle screen. In addition, you can’t put sprites with different cell heights in one sprite sheet. If you go to 'edit sprite' you will see that the maker divided the gif into the different frames present. (This is when the “$” is used, and this is primarily for singular sprite sheets) When you create a new sprite in gamemaker choose 'load sprite'. 1st row is down movement, 2nd row is left, 3rd row is right, and 4th row is facing up.

The way you can use those is up to you, but if you look at the default sprites this shows an example of how the program reads them. Rpgmaker’s sprites are supposed to have 12 equal cells split into 4 rows and 3 columns. Undertale was not made in rpgmaker so the way those sprites have been formatted are not compatible with the way rpgmaker reads sprites.

Elemental sprite sheet RPG Maker MV