align-default-spacing is a variable defined in `align.el'.
Its value is

An integer that represents the default amount of padding to use.
If `align-to-tab-stop' is non-nil, this will represent the number of
tab stops to use for alignment, rather than the number of spaces.
Each alignment rule can optionally override both this variable and
`align-to-tab-stop'. See `align-rules-list'.

You can customize this variable.