Hello!

Specific charge means= charge to the ratio of the mass

Let, Electron charge=e and Electron Mass=m

We know the following,

Alpha Particle's Charge= 2e and the mass is 4m

Electron's specific charge = e/m

alpha particle's specific charge = 2e/4m

Therefore, specific charge of electron to the alpha particle= 2:1

Hope it's clear now.