Why do you use 说明称, not either 说明 or 称? According to this news over 中国新闻网:

中新网10月4日电 据日本媒体报道，日本新党“希望之党”党首、东京都知事小池百合子3日再次否定自身会参加众院选举，称“百分之百不会，从一开始就这么说”。
小池说明称，前首相小泉纯一郎对她说“作为都知事加油”。她断言道：“虽然(小泉)进次郎叫着(要我参选)，但我向他父亲承诺不会出马。我将作为都知事继续切实努力。”

What is the meaning of 说明称? 说明 means &quot;explain&quot; while 称 means &quot;call&quot; or &quot;say&quot;. So I feel that the words are duplicated.
What I don't understand is why it duplicates the words as 说明称. Why not use just one, which I think enough...?
BTW what is the meaning of 从一开始...? Why is it not 从开始? Well I might pose a separate question...
说明 is used as a noun word here, meaning 'illustration or explanation'. 

So, 说明称 means 'say in her/his illustration/explanation'. 

从一开始 means 'from the very beginning', while 从开始 means 'from the beginning'.