How to determine the units used in odom_combined and Twist on Turtlebot Kobuki?

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I am attempting to figure out how the measurements received from the rostopic, odom_combined (geometry_msgs/PoseWithCovarianceStamped) relate to real world units. For example, when I input the following command: rostopic echo odom_combined. I received the following output

pose:
   pose:
       position:
           x: -0.9762
           y: -2.1532
           z: 0.0
       orientation:
           x: 0.0
           y: 0.0
           z: -0.6230
           w: 0.7821

I think that orientation is in radians, but I cannot figure out the units of position. I moved the turtlebot from x: -0.9762 to x: 0.9762, but, when I measured the actual distanced moved, I got 12 feet 7 inches.

I am also trying to figure out the units of twist. I think that orientation in twist is in radians per second, but I do not know what units position is in.