Smart Playlist on iPhone unexpectedly trimmed down.

I have a Smart Playlist of my favorite songs, about 300 songs. I maintain it on my iMac and sync it to my phone. Today I noticed the playlist on my phone was all of 9 songs.

The simplest thing seems to be re-sync the computer and phone. Question: How do I make sure the phone is updated back to 300 songs and the computer is NOT updated to 9 songs?

Thanks,

Jeff