bug? or operator error?

I created a form: Job, with job.job_ID and a bunch of other fields. Then I created a form: Job Progress, with a Job ID lookup field where I use a dropdown list to enter a value from job.job_ID.

I imported about a dozen Jobs records into the Job table. I proceeded to create Job Progress records for each of those, by picking a value from the job.job_id drop down list (and assigning values to various progress related fields in the Job Progress table). Each record was successfully created in the Job Progress table, but each job progress record also created a new row in the Job table! with identical value as the job.job_ID record. According to the Job view
Weird.
So I went to delete these dozen or so new rows in the Job table, and after I did so, my original dozen or so Job records now have no value in the job.job_ID!

did I do something wrong in my design? or is this some kind of weird bug?
cpstrisha