Perhaps your concern relates to the different ways that voltage is expressed in the practice of circuit analysis. Voltage is really only a useful concept as a voltage difference (i.e. the voltage across a resistor). In a circuit example that includes finding the current in a resistor, there is no real difference in that current between a voltage drop from 1002V to 1001V as from 2V to 1V or 1V to 0V. However, to make it easier for us to write and solve equations, we will often use a single voltage which is implicitly referenced to a very specific single voltage in the circuit. We would normally call this voltage "ground" and define its value to be zero.
So, The simple example I drew below shows how these representations are equivalent, provided you understand that the "ground" voltage ##V_0## has been defined to be zero and thus left out of the equations.
Also, once the ground voltage has been define to be zero, that applies to all of the circuit elements connected to that node. So this is the same as saying the emitter voltage in your circuit is defined to be zero and thus ##U_{BE}## could also be referred to as the base voltage (with respect to ground).
As a matter of style, to avoid confusion, I really dislike mixing the variables named ##U## and ##V## to express voltages. It is much easier to read the equations if there is a common standard notation.
Finally, I will add that in many decades of working with circuits like this, it has been really common for me to simply redraw and rename things in the circuit to match my preferred definitions. Otherwise things can get unnecessarily confusing.
