What is a consecutive digit?

There's no such thing as one consecutive digit. There has to be at least two of them.

When you count, consecutive digits are numbers that you name in a row, with nothing else between them.

Examples:

34 and 35 are consecutive. There's no counting number between them.

97 and 98 are consecutive. There's no counting number between them.

62 and 64 are not consecutive, because 63 comes between them.