Here one determines the minimum free disk space required for the drive on
which the auxfile will reside. The number given is in bytes, in Kbytes (if
the letter `K' is added) or Mbytes (if the letter `M' is added). The default
is {20K}. The second parameter specifies the minimum amount of free
space required, above the size of the current bibliography file. The default
is {4K}. The minimum allowable free space will be the maximum of the
first number and the size of the current bibliography file + the second
number. The third parameter specified the minimum amount of free space
required for the second (list) auxiliary file. This file consists of a list
of the names of entries in the main bibliography file, and is therefore much
smaller than the main file. The default for the third value is the value of
the first parameter.