In Varphi, a tally represents a tape cell containing a tally and is denoted by the character 1. A blank represents an empty tape cell and is denoted by 0.
The concept of a blank in Varphi is not to be interpreted as adding a new possible tape character. In the strictest sense, there is only one possible character in the alphabet of Turing machines, and that is a tally (given by 1 in Varphi). But if a tally is not present in a tape cell, then that tape cell is blank (represented using 0 in Varphi), and does not contain any tape character.