Good question, although I'm afraid the answer is only pseudoscientific. I modelled the logo after a chemical element symbol. Typically you express the mass of an atom with a decimal point because it's an average of masses. You take all the different versions of an atom and the average mass is what ends up on the PTofE. There aren't multiple versions of me (that I know of) so that number isn't an average of my mass. My mass is 70 kg but 70 on its own looked boring.
The symbol at the top is not a trident (as some of my Physicists suggested). It's a greek letter psi and it's used in Science to represent what's called a "wavefunction" - a full description of a particle/group of particle's behaviour and state at any one point in time. I, as a collection of particles, can be described by a wavefunction, hence the choice of symbol!