chapter.autolabel — Specifies the labeling format for Chapter titles
If non-zero, then chapters will be numbered using the parameter value as the number format if the value matches one of the following:
Arabic numeration (1, 2, 3 ...).
Uppercase letter numeration (A, B, C ...).
Lowercase letter numeration (a, b, c ...).
Uppercase roman numeration (I, II, III ...).
Lowercase roman letter numeration (i, ii, iii ...).
Any nonzero value other than the above will generate the default number format (arabic).