I'm just guessing but here's what i think:
(by the way the image you posted doesn't look like a battler, more like character sheet but anyway)
So RMMV chops up your images horizontally dividing it by whatever preset amount of frames an animation does right
So for example there are 3 frames per walk downward animation (i think, check the existing character spritesheets).
The sprite image's width is "frame width x 3". If per frame you have 48 pixesl for your person, that will be 144px wide. height will be "frame height x 4" which is like a row for walk down, left, right, up.
So now if your person isn't centered properly, in that 48 frames (144px over 3), RMMV will display it like what you have above.
I would suggest modifying your images so that your character is centered. (yes its a little bit more work)
|----- 48px ------|
| \o/ | <--- the first and last pixel of the character's hands should have the same amount of distance from the edges of the frame
| ||| |
| / \ |
|------------------|
|----- 48px ------||----- 48px ------||----- 48px ------|
| \o/ || \o/ || \o/ |
| ||| || ||| || ||| |
| / \ || / \ || / \ |
|-------------------||------------------||------------------|
I dont have access to anything at work right now lol but i hope you get what i mean.