Definitely turn off mixing if you're animating things that are that fast and short. Set the Default Mix
on your SkeletonDataAsset inspector to a very low number, or 0.
If your animation is 7 frames on the dopesheet, that's 7/30 seconds (0.233~). If you didn't change the default mix, the mix would have taken 0.2 seconds, which is already pretty much the duration of that animation.
Note that it's not only mixing out of the previous animation, but also mixing into the next one. That's theoretically 0.4 seconds of transition time that a 0.233 second animation doesn't have.
Higher mix values generally make movements more muddy and make short animations like this unusable. You can define individual mix values between each pair of animations in the SkeletonDataAsset inspector.
Also as a general rule, even if mixing is disabled, the first "frame" is never visible. This is a characteristic of game engines and realtime continuous animation as opposed to frame-based ones. Despite the frame numbers on the dopesheet, the Spine runtime deals purely in terms of seconds and game update times cause the pose at time 0 to never be visible unless you modify the code to show it, but that would have the sideeffect of causing time inaccuracies.
You need to give it 1 or 2 frames in the dopesheet for that first pose to be kinda visible.