A table cells are indexed according to a placement within the table's columns and rows.

The best way is show indexing on examples.

Standard tables

In a standard table numeration of cells is straightforward and zero-based. The first cell in a table is indexed as 0,0 (column 0, row 0). For example, the cells in a table with 4 columns and 4 rows will be numbered accordingly:

Merged cells

If we merge 2 pairs of cells (1, 1) x (2, 1) and (1, 2) x (2, 2) then table will be numbered and look like this:

Let's continue merging cells. Now we merge (1, 1) and (1, 2). As a resuly we have table with large merged cell in the middle:

Cell splitting

We could see in previous example when table cells are merged then numeration of other cells is not changed.

Now let's return to our normal table (without merged cells) and try to split cell (1, 1). The result is strange enough but that is the way MS PowerPoint and Aspose.Slides numerate table cells: