RO (without DI) does not remove everything. With an advanced setup like with a booster pump and a 5:1 waste ratio and a high quality filter you would probably see a 95% reduction.

But without a booster pump or if you've got a lower waste ratio either by restriction or piggyback ro membranes you'll have a lower rejection rate.

And that ignores the fact the you really need to be back flushing the membrane regularly and rejection rates are measured after 30 minutes of continuous running, ions migrate when it's idle so you have to throw away a lot of water at the start that you're probably not doing