Safety Stock Fomula

Good Day,

I cannot understand how SAP calulates Safety Stock and Reorder Stocks?

It gives me

8057 Reorder Stock

3464 Safety Stock

5790 Minimum lot

Here some MRP Parameter:

Periods 12

Service Level: 70%

MRP ZL

Lead time: 21 + 2

External source

Moving Average

History of consuption From last to least recent (8780,14150,11520,7540,10300,6430,4070,435,265,1220,2060,2705)

Thanks in advance for any reply.MB.