2.1.527 Part 1 Section 17.18.14, ST_DocGrid (Document Grid Types)
a. The standard states that the snapToChars attribute serves the same purpose as the linesAndChars attribute.
The snapToChars attribute specifies that each line in the parent section shall be divided into units of the character pitch specified on the docGrid element ("[ISO/IEC-29500-1] §17.6.5; docGrid"). Contiguous regions of characters u as eastAsia, ascii/hAnsi, and cs using the character classification algorithm are then placed into these units as follows:
eastAsia – One character per grid unit, centered in that unit.
ascii/hAnsi – All characters in the block centered in as many grid units as are necessary to display that text. [Example: If text needs 4.1 grid units of space, it is centered in 5 units. end example]
cs – All characters in the block left-aligned in as many grid units as are necessary to display that text.
The additional line pitch on the docGrid element is also added in order to maintain a specific number of lines per page and characters per line.