Hi, I dont have experience of this company but other companies also mention this kind of phrase, that means that within the working hours of the day, your product would be delivered, this is what I understand by this phrase.
When Amazon deliver to me (Prime service), the initial email states delivery "by 9pm". As the day progresses, the time becomes more specific...."between 1.45 and 3.45pm" and then..."six stops away....five stops away" etc.