>The customer sent me an email indicating that the server (hosting SQL Server) has 8 GB. And the value in the Maximum memory is 2147483647 MB. Does it mean they have no limitation? Or, should the Maximum memory number should be changed to?

?2147483647/1024**2
gives 2048, so that limitation is set to two terabytes. It's still a limitation, although a bit above the physically possible.