#!/usr/bin/perl -l

$text = do { local $/; <DATA> };
print $1 if $text =~ /
   ^Total\s+Datafile\s+Size\s+MB\s*     # header
   ^-+\s*                               # separator
   ^([\d.]+)                            # the number I want
/mix;

__DATA__

Total Datafile Size MB
----------------------
73602.1406


Total Database Size MB
----------------------
48107.7656


Total Free Space MB
-------------------
25462.8125