You can choose Fit at the Size section on the export settings window, then enter your desired size. When Pad checkbox is checked, additional space is added to the image to match the specified size, so you can export animations at the desired size.

Misaki wrote

You can choose Fit at the Size section on the export settings window, then enter your desired size. When Pad checkbox is checked, additional space is added to the image to match the specified size, so you can export animations at the desired size.

Yeah, thats for .gif, but i need it in Binary
Is there a way? Or does gif settings affect that one in binary section?

When exporting skeletons using binary format, the size of the displayed animation is determined at runtime. Just to confirm, you are not saying that you want to specify the size of the texture atlas page, right? If you want to specify the texture atlas page size, you can do so by setting Max width/height and Min width/height to the same value in the texture packer settings.

Misaki wrote

When exporting skeletons using binary format, the size of the displayed animation is determined at runtime.

thats exactly what i was interested in!
But i can't quite get it, can you exlain it to me? What does it mean "determined at a runtime"? Does it mean that the animation in binary have no certain size(border) at all like regural video or gif? It only contains the infromation about bone movement?

Does it mean that the animation in binary have no certain size(border) at all like regural video or gif? It only contains the infromation about bone movement?

Rather than having no borders, it would be better to think of the bounds as being variable to match the pose while the animation is playing. The method of determining the bounds depends on which runtime you use and how your skeleton is implemented. For example, in the case of Spine Web Player, by default the bounding box is automatically calculated for each animation, but it is also possible to specify the viewport size and trim any animation outside the size:
Spine Web Player: Viewports

Also, you can scale skeletons at runtime to display larger or smaller sizes. Please see the Spine Runtime Guide for general information of Spine runtimes:
Spine Runtimes Guide

Misaki wrote

Does it mean that the animation in binary have no certain size(border) at all like regural video or gif? It only contains the infromation about bone movement?

Rather than having no borders, it would be better to think of the bounds as being variable to match the pose while the animation is playing. The method of determining the bounds depends on which runtime you use and how your skeleton is implemented. For example, in the case of Spine Web Player, by default the bounding box is automatically calculated for each animation, but it is also possible to specify the viewport size and trim any animation outside the size:
http://esotericsoftware.com/spine-player#Viewports

Also, you can scale skeletons at runtime to display larger or smaller sizes. Please see the Spine Runtime Guide for general information of Spine runtimes:
http://esotericsoftware.com/spine-runtimes-guide

Thank you

You can find a documentation of what is described in the JSON export format the following page:
Spine: JSON export format: Skeleton

Here is the quote:

width: The AABB width for the skeleton's attachments as it was in the setup pose in Spine. This can be used as a general size of the skeleton, though the skeleton's AABB depends on how it is posed.
height: The AABB height for the skeleton's attachments as it was in the setup pose in Spine.

As the documentation describes above, only the setup pose is used to determine the width and height values, so no matter how you create large poses during animations, these will not be changed.