2.2.6.1 XFs
XFs specify formatting for cells and cell styles (section 2.2.6.1.2).
XFs are specified by BrtXF (section 2.4.862) records. BrtXF records specify font, fill, border and number formatting via indices into the FONTS (section 2.1.7.50), FILLS (section 2.1.7.50), BORDERS (section 2.1.7.50), and FMTS (section 2.1.7.50) collections. Alignment and protection properties are specified directly in the BrtXF record.