[Solved] Last characters of a string / string 'slice'?

So, I've found out that you can find the length of a string in Roblox Lua in a similar way as to how it's done in Python (using .len). However I can't seem to find anything on string 'slicing' or selecting a specific range of characters to pick out from the string...

For example in Python to select the last 4 characters of a string you'd use [:-4] however this doesn't work in Roblox Lua...

Any help would be much appreciated! Thanks :)