After introducing a simple scale from 0-4, I use this as a way for my students to rate their understanding. Each child is assigned a numeral and each child rates their understanding according to the scale. A free scale can be found on my blog or other versions can be found on TPT, Pinterest, etc.
My students will document their beginning, middle, and ending numbers on a graph in their data rings. Recording sheets and data tracking sheets are also included. Some of these are also editable in powerpoint format.