Transposition error
From ACT Wiki
1.
A simple error of data entry when two digits in a number are reversed (transposed).
When two adjacent digits are transposed the error will always be divisible by 9.
For example: If 3,460 should be 3,640 the difference is 180 (3,640-3,460=180) 180/9 = 20.
2.
Similar errors with non-numerical data. For example ABC entered wrongly as ACB.
