You can preview slices of your animation on the Time View tab of the Animation Manager. To do so, click the Time View tab and click in the below the time line to expose the red slider, and to view the recorded county population near the beginning of the animation.

The space between each tick mark on the track line represents each 10-year period. After the second tick mark, the time slice displayed will change from 1800 to 1810. Note the animation time (from 0.000 to 1.000) at the bottom of the Time View display. All tracks operate within this animation time.

Click further along the time line to view a time slice near the middle of the animation. Notice that many more counties are recording population as time goes by.

Click near the end of the time line to view the time slice for the 10-year period after 1990.

With Restore state after preview checked, closing the Animation Manager would remove the time text and the layer would go back to its original state. The current definition query set to show the time slice for 1990 would be removed.