This call option model is based on the Black-Scholes model. For more information use Help Seacrh command to look up functions, then look up the STEquityCallOption function.
The time to expiration, the desired rate of return and the variance must reference the same time scale, therefore, since the variance was calculated on the avearge share value over the last six months, the days to expiration are expresses as a fraction of 180 days (six months) and the annual rate of return is divided by two (for a six month rate).
