This is a Unary Number System variation that is popular in China, Japan and Korea. The full Character (Cheng) means honesty or correct according to the Wikipedia Tally marks article.
Something I neglected to mention in the first Unary Sudoku Cartoon is the Encyclopedia of Integer Sequences which contains within it the table of the first 1000 Unary Numbers! This table was created by David Wasserman. While this is something of a non-computational table, it turns out to be really handy when you need to copy and paste the Unary number elsewhere, rather than count the strokes yourself.