Phone Conversations

My husband will add on the time we spend on the phone to discuss something to the time he finishes his tasks. We have small children and I might need a hand, and instead of "I'll be done to help you at 6:00" it will become "I'll be done at 6:04" because of the time I spent explaining to him what I needed on the phone. No one I've met does this. AITA for just wanting him to stop doing this? Note - he's usually later than the "6:04" example anyway.