The Original Black-Scholes Model
The original Black-Scholes option pricing model (Black, Scholes, 1973) assumes that the underlying security does not pay any dividends. In other words, dividends don’t enter option price calculation in any way.
Black-Scholes (-Merton) Model Expanded for Dividends
The spreadsheet uses the expanded version of the model (Merton, 1973) that can price options on securities that pay a dividend. The calculation assumes that the underlying security pays a continuous dividend at the rate you set as entry parameter.
Note: If you want the exact original Black-Scholes model, just set dividend yield to zero.