Lots of spit up after first formula feed

My LO is 6 weeks old and I have been doing all the things to try and keep her exclusively breastfed, but my milk production is just not where it needs to be. Today I decided to try a formula feed. I did 2oz and she took the whole thing no problem. Slept for 3 hours. Woke up, nursed for 30 minutes and was super calm. 15 minutes later she spit up an insane amount of milk and repeated that again in 5 minutes. Was not agitated by it at all. Any ideas if this is normal for the first intro formula feed? Just had a bm, so she’s not backed up.