How it works
A bead is worth one, ten or a hundred, depending on the row it sits on.
The bottom row counts ones, the middle row counts tens and the top row counts hundreds.
Each step up a row makes a digit worth ten times more, so a three can be 3, 30 or 300.
An empty row is a zero, and the zero keeps the place. Without it, 205 would look like 25.