2 Schedule lines in STO even Stock is available

Dear MM  Expets,

I have configured STO SLoc to SLoc configuration for client.

ATP is also activated.

Assignment of Del type and checking rule and Del type and checking rule According Storage location is also done.

All necessary config is done.

When I am entering quantity less than available stock for ex: Available stock for supplying plant 2049 SLoc 0001 is 200 and am entering 50 quantity in STO del date 01/10/14 then system is showing 2 schedule lines.In second schedul line 50 quantity is showing as commited quantity and del date is 1/10/14.

My query is if stock is available at del date why system showing 2 schedule lines.

Regards,

Abhijeet.