The simulator runs 10,000 hypothetical price paths under Geometric Brownian Motion (GBM) — the same stochastic process that backs Black-Scholes options pricing. Each path takes daily steps; at each step the price drifts by your annual-drift assumption and gets randomly shocked by your volatility.
S_{t+1} = S_t · exp((μ − σ²/2)·dt + σ·√dt·Z)
Z ~ N(0,1)
μ = annual drift
σ = annual volatility
dt = 1/365After all 10k paths complete, prices are sorted by day and the 10th / 50th / 90th percentiles are extracted to draw the cone. The terminal-day distribution becomes the histogram.