Slow copying over internet

I am doing offsite backups for my work. Currently I'm using SyncBack Pro on the client side(Windows . The server side is a synology diskstation. I am using SFTP to connect to it. If I download a file manually using FileZilla it downloads at my max download speeds about 1.8mbs but if I have SyncBack download it it will average out at about 300K/s

Any suggestions.


NOTE: I can install any server on the synology diskstation.