For example, let's say someone says
いつでもいいよ!
In English I would just simply say, "okay, sure, alright" just to tell the speaker I heard what they said.
I initially thought to reply with はい but that doesn't feel right, it feels like はい is more of a confirmation than simple acknowledgement.
Is はい the proper term to use to acknowledge this kind of statement? What other ways can I acknowledge someone said something?