How to use Deduplicate snap?

I plan to use Deduplicate snap to remove duplicate records from a CSV file. In my CSV file, let’s say I have 3 records with the same ID. I just want to keep 1 record.

So I am using Deduplicate snap and set it up like this

It works but it also remove some of the not duplicated records. Why?

The thresholds in the snap default to values suited for approximate match. For exact match, you can set a higher threshold, like 0.9 and set a low criteria of 0.01 and high of 0.99