Hello @uiStijn
I would recommend you to stick with your pattern (?<=W57209.)[\d\W]+ as the other pattern are including ISO numbers as well (11731 etc.), which might return unexpected results:
You can do below
log message =
(from val in String.Join(" ",(from m in Regex.Matches(str_PDF_Data,"(?<=W57209.)[\d\W]+").Cast(of Match) select x = Regex.Replace(m.Value.Replace(">15000","15001"),"[^0-9. ]","")).ToList).Replace(" "," ").Split(" "c).ToList select x = CDbl(val)).Max
You can replace 15001 with anything that you want.