The numbers 4480 and 704 are the default number of worker threads that SQL Server will create if you leave the configuration "Max worker threads" at 0 (4480 for 128 processors and 704 for 16 processors).
That being said, you can override this default behavior by specifying the number of worker threads you need. For instance, you can set the number at 1024 by running these commands:
exec sp_configure 'max worker threads', 1024;
reconfigure with override
Basically, you can set this number as high as 32767. BUT, you will probably run into troubles if you set it this high. On some of our SQL Server 2014 servers (Standard Edition), we have set it as high as 3072 (we have a lot of concurrent connections) without problems. You just need to make sure you have enough RAM to handle the worker threads.
Hope this helps.