If there is a minus symbol on a seed, should I ignore that when I put a seed in the "server.properties" file?
Solution 1:
you need to keep the '-' sign.
discrepancies in world appearence can be because of spawn coordinates, minecraft version or mod list/mod config. Make sure to use the same 'environment' as the videomaker and /tp to the coordinates that video was recorded at.
Solution 2:
Try to create the world in your local client, and then copy it on to the server world. Remember to put the correct seed in level-seed=
Edit 1: You need to put the minus symbol