If you have set a sow to be given a 2nd litter after her first weaning (made a nursing sow by ticking the box on the weaning screen), she can be weaned as normal on the weaning data entry screen by giving her a date and the number of pigs weaned off her (2nd weaning). Once this has been done, you are now free to give her a service or cull date (if she is being removed).
The above example shows 1315 being weaned on 23/02/21 with 9 pigs. She was made a nursing sow (tick in box) and 11 pigs were fostered on to her (optional). She was then weaned for a second time on 02/03/21 with 10 pigs. The nursing sow box is left blank this time as her litter is complete and she is available to be served or culled.
If you do not use the "transferred piglets" option, your screen will probably look more like the one above