This attribute specifies how many digits of precision are
required by default when a coordinate value is formatted for a
FrameFrame axis (e.g. using astFormatastFormat). Its value may be set either
for a Frame as a whole, or (by subscripting the attribute name
with the number of an axis) for each axis individually. Any
value set for an individual axis will over-ride the value for
the Frame as a whole.
Note that the Digits value acts only as a means of determining a
default Format string. Its effects are over-ridden if a Format
string is set explicitly for an axis. However, if the Format
attribute specifies the precision using the string ".
", then
the Digits attribute is used to determine the number of decimal
places to produce.