Is it normal for Vanguard to sell shares of a target date fund automatically and send it to my settlement fund?

I received a text saying: “Vanguard Msg: A $ (I just removed the actual number) transaction was submitted from account ending in 1111 to your settlement fund. Reply STOP to cancel txt msgs”

I didn’t create this transaction. Why would Vanguard be doing this? I’ve only had a Roth IRA with them for less than a year, so this is new to me.