To be clear, they are calling out the number that indexes the papers, not a name of a person or a name of a candidate. 一號, 二號, 三號….

正 is the tally mark https://en.wiktionary.org/wiki/%E6%AD%A3

I have like a 1-2 year old's level of Mandarin at this point, sigh, but I don't think there is a detail I'm missing once the process gets going. This is a good, accessible voting system.