Solution : https://service.sap.com/sap/support/notes/197300 (SAP Service marketplace login required)
Key words : 
program lm61wtop set, program mm61wtop, terms mp30, mm02 solution, implement notes 350555, corrections, schwelle_rundung, rounding_threshold
Related Notes : 
       
| 93765 | Forecast values: rounding decimal places | 
| 69653 | Material forecast: Values < 10 not rounded |