Add the following on page "4.4. Page TSConfig" in Table "Properties of each class available in the RTE." inside the description columns after the .alternating Section:
( http://typo3.org/documentation/document-library/extension-manuals/rtehtmlarea_manual/1.7.4/view/4/4/ )

# specification of couting classes for rows and/or columns of a table
.counting {
	rows {
		startAt = int (default = 1)
		rowClass = class-name
		rowLastClass = class-name
		rowHeaderClass = class-name
		rowHeaderLastClass = class-name
	}
	columns {
		startAt = int (default = 1)
		columnClass = class-name
		columnLastClass = class-name
		columnHeaderClass = class-name
		columnHeaderLastClass = class-name
	}
}

Add the following example:

RTE.classes.countingtable {
	name = countingtable
	alternating {
		rows {
			startAt = 1
			oddClass = tr-odd
			evenClass = tr-even
			oddHeaderClass = thead-odd
			evenHeaderClass = thead-even
		}
		columns {
			startAt = 1
			oddClass = td-odd
			evenClass = td-even
			oddHeaderClass = th-odd
			evenHeaderClass = th-even
		}
	}
	counting {
		rows {
			startAt = 1
			rowClass = count-tr-
			rowLastClass = count-tr-last
			rowHeaderClass = count-thead-
			rowHeaderLastClass = count-thead-last
		}
		columns {
			startAt = 1
			columnClass = count-td-
			columnLastClass = count-td-last
			columnHeaderClass = count-th-
			columnHeaderLastClass = count-th-last
		}
	}
}

Hint: Use class name prefixes for the counting style, that are not a substring of any other class name.