Well in general for testing I'd recommend Rubular.com or a Regex Testing tool from Rad Software
http://www.radsoftware.com.au/regexdesigner/
extract the number which can be done in many way depending on what exactly you are trying to parse.
See Rubular link for your particular example
http://www.rubular.com/r/GeJRrZS7E1
The pattern is
^<span.*?>(\d*\.\d*).*<\/span>$
Now the explanation
From the start of the line
(^ character)
You need to have "<span" characters
Followed by some other characters until the ">" character
(it is done by using .*? non greedy technique which takes character after character (?) and sees if it matches)
Now you'll have 0 or more digits followed by a point and than followed by 0 or more digits
(\d*\.\d* - it is also saved with the parenthesis)
Followed by 0 or more characters
(.*)
Until "</span>" characters
And the line should end here
($ character)