Ruby method to generate a .hyv header row checksum

hyv_checksum.rb

#### HYV EXAMPLE HEADER ROWS
lines = [
  "Champs Final 2010;06/27/2010;06/27/2010;05/01/2010;Y;UT Swim Center;;Hy-Tek Sports Software;2.0Hm;CN;7116a",
  "Time Trials Summer 2012;05/19/2012;05/19/2012;06/15/2012;Y;YWSC;;Hy-Tek Sports Software;4.0Cf;CN;9111m",
  # hyv_checksum generages 0141a for this case (the rest work)
  "Peakhurst Junior Sprint Meet 2011;05/22/2011;05/22/2011;05/22/2011;S;Peakhurst Pool;;Hy-Tek Sports Software;3.0Cj;CN;1141a",
  "2011 Indian Ocean All Star Challenge;04/23/2011;04/24/2011;04/23/2011;L;Challenge Stadium;;Hy-Tek Sports Software;3.0Dv;CN;21461",
  "2009 JSL CHAMPIONSHIP;07/30/2010;07/31/2010;06/01/2010;Y;UVA AQUATICS CENTER;;Hy-Tek Sports Software;2.0Hm;CN;61180",
]

# hyv_checksum generates a header row checksum for a .hyv file.
# The algorithm contained is very close to correct, but not quite
# as test case 3 above has one incorrect 1 character.
def hyv_checksum(values)
  # Compute the sum of the ascii integer code for each character
  ord_sum = values.reduce(0) { |sum, v| sum + v.ord }

  # magic1 because who knows why we do these things
  magic1 = ((ord_sum.to_f - 1) / 7).round(half: :even) + 205

  # Turn magic1 into more magic... a string of 4 characters, prepending blanks if needed
  magic2 = '%4.4s' % magic1.to_s

  # Sample some characters out of magic2 and the original string to achieve even more magic and victory
  magic2[3] + magic2.slice(0, 3) + values[2]
end

lines.each do |line|
  # get the raw values
  raw_values = line.split(";")
  # pop off the checksum and save it for later comparison
  checksum = raw_values.pop
  # compute the checksum
  computed = hyv_checksum(raw_values.join.split(//))

  puts "raw string: '#{raw_values.join}'"
  puts "Original Checksum: '#{checksum}'"
  puts "Computed Checksum: '#{computed}'"
  puts checksum == computed ? "✓ correct" : "✖ wrong"
  puts "\n------\n\n"
end