using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var text = "Top Rate: 8                      88,888 and Top Rate:                       8  \n   88,888 Top Rate:     2,500.00";
		var results = Regex.Matches(text, @"\bTop Rate\b.*?(\d(?:[\d,.\s]*\d)?)", RegexOptions.Singleline)
			.Cast<Match>()
			.Select(x => new string(x.Groups[1].Value.Where(c => char.IsDigit(c) || c == '.').ToArray()));
		foreach (var s in results)
		{
		    Console.WriteLine( s );
		}
	}
}