I've selected Naubis resource generation in the settings and reduced the resource frequency to the absolute minimum, but when I start the game, it seems to generate more resources than any other resource.
Am I missing something? Please let me know how to fix this.
It's seriously ruining the game balance.
Please help. I really want to try this mod, but it's overgenerating.

You're saying you are using the "Tiberium Initially Spawns On: Nauvis has Tiberium" mod setting, default scenario, and turning down the frequency of Green Tiberium Fields on the resource tab?
If the issue is that you think too much Tiberium Ore is growing, you can also turn down the size slider which will reduce the number of Blossom Trees per patch. This will reduce the growth rate, since each tree spreads Tiberium Ore at a fixed rate.
If the issue is that you think converting the Tiberium Ore into other resources generates too many resources, you can also use the size slider or you can put a smaller number in the "Tiberium Recipe Value" mod setting.
If the issue is that there are certain modded ores that are supposed to be rare and they are being given out like candy by the Tiberium recipes, you can correct that by listing them in the "Exclude Specific Resources" mod setting

Hello. Thank you for your reply.
When I start a new game, I add Tiberium to Naubis in the mod's starting settings and lower the Tiberium resource spawn rate to the lowest slider in the Map Settings' Resources tab.
However, when I start a new game, I find Tiberium spawning in too many places on the map.
Even with the spawn rate reduced to the lowest, Tiberium is still easily found everywhere with just a little exploration.
I personally wanted this wonderful Tiberium ore to be like a real-world diamond, where it's hard to find, but when you do find it, you'll be cheered on.
I use the default settings for this mod with almost no changes.
I simply lower the Tiberium resource spawn rate in Naubis to the lowest in the Map Settings' Resources tab and start with a slightly increased abundance.
I use a machine translation, so please understand.
Thank you.

With those settings, I'm seeing 1-5 Blossom Tree clusters being generated in a 2000x2000 area around spawn, which is rarer than uranium.
On default settings, we spawn Tiberium at the same frequency as Crude Oil, and the slider does not go far enough to turn that into "diamond rarity"
You can use the Patch Size slider to reduce the total about of Tiberium Ore or the Tiberium Recipe Value setting to increase the amount of Tiberium Ore you will need for recipes, but there are no settings to make it as rare as diamonds.
If you are only player single player, you can open the Factorio-Tiberium_2.0.13.zip file from your mods folder and edit line 221 of /prototypes/resource.lua to say:
base_spots_per_km2 = 0.2,

Okay, I'll play with the solution you mentioned :) Thanks for the great mod.

In my game, Tiberium spawns in a huge number of places.
It spawns every 20 chunks, sometimes every 30.
So I thought it was excessive, but I suspect it's probably a mod compatibility issue with my heavily modded game.
It could also be an issue with the RSO mod.

Oh, RSO will do that. I was under the impression that most people stopped using RSO after 0.17 and started using the Rail World scenario.
I see that they now have an API for excluding resources and planets, so I'll update it so RSO doesn't change Tiberium spawning in 2.0.14