Q: Why the actual simulator results may differ from those in my calculation?

A: There are several factors leading to the plan/fact discrepancy:

• The most significant factor is that usually you cannot predict demand with 100% accuracy, so there are unsold inventories. This decreases your fact revenue against the planned one and affects many other Balance Sheet, PnL and Cash Flow items. If the real sold quantities are known, using them (rather than safety stock quantities) to prepare the calculation will produce much accurate results
• Neither you exactly know several other factors affecting the results: percentage of rejected products and guarantee returns, for how long your employees are sick or absent, machinery efficiency and reliability etc. Most of these parameters will differ from zero, so enter your best guesses in the Assumption section. On preparing a new calculation, you upload the fact management report of the previous period, where the default values are taken from. Using these defaults are good starting point in the elaboration of your decision, cause usually these parameters do not fluctuate much from quarter to quarter.
• Collection of Accounts Receivable (Trading receipts) contains a random variable. Usually the company collects 1%-2% less or more than expected. This reporting item affects some others like Credit Control, Net Cash Flow, Cash Balance etc.
• The model does not try to predict other random events like employing temporary external assembly workers, insurance claims and reimbursement and others.
• Different rounding approaches (although leading to smallest discrepancies).
• ???In the initial period incoming inventory valuation per product is not known and calculated approximately.
• And yes, there might be bugs in our model. So if you notice one, reporting it will help to improve the model's quality.