New phone (from AT&T) and cellular usage out-of-the-box

This is *probably* answered somewhere but I could not find it by keywords. I got a new iPhone 6 to upgrade from my 2-year-old 5, via AT&T. Ordered it about a month ago and it finally shipped late last week and arrived last night. Shrink wrapped, brand new. Serial # indicates it was made just a couple weeks ago (via that lookup site I found somewhere). I restored my icloud backup before I checked this, but... In Settings->Cellular, it had (right after the restore and upon my first "dorking around" with the phone) about 5 hours of "Call Time" in both current period and lifetime. Why wasn't that zero? Is that from factory testing, an artifact of my restore, or what?