I see you got your answer - If I am doing a doily, I usually make sure that I use the 5000m spools - I don't want to take the chance of running out and ruining what I have done. Plus, you have to have the same thread in the bobbin. I was doing a fsl project once, and did run out. It was a varigated thread, and I did not read the yardage right. I had to run back into town and hope tht they still had another spool of the thread. That spool only had 600yds on it and not 600m as I thought. I had bought 2 - but needed 3 to do the project.
We'll ask the experts. Hope this helps, now many stitches in your doily?