300Gbps? Is that typo? Unless you are connecting to some very particular infrastructure on the other one, nothing you could possibly connect to could use it, and you would need gear that would be somewhat high end even for server grade.
(I know you said you didn't select that option, but just the idea that it's even offered to residential units is mind blowing).
Usually there is a 300 Mbps - 10 Gbps range of offerings.
No, not a typo. Ziply has 300 Gbps at my house if I want to pay $900 a month. Instead I pay $65 for 2 Gbps