Hii,
As correctly said by Sharat Any demand falling below 20 or between multiples of 20 for the material you used will create demand in multiples of 20 as you used rounding value. See below details from SAP
Rounding value for purchase order quantity
Value to a multiple of which the system rounds up the procurement quantity.
Dependencies
The rounding value is used in the planning run if no rounding profile has been specified in the material master record.
as your rounding value is 20 system will create demand in multiple of 20. if your rounding value,suppose, 30 and md61 having requirement 70 then demand created by system will be 90.
Please check and revert.
MDS.