Worked example: payor $201,000, recipient $29,640, 3 children, Box 1, child care $300/wk paid by recipient
Base order (no child care)          $1,013/wk  $52,662/yr

1.  CURRENT (Line 3c, pre-transfer)       payor funds  87.7% of child care (+$13,678/yr; order $1,276/wk)
2.  POST-TRANSFER GROSS shares            payor  64.3% -> funds $10,033/yr
2b. POST-TRANSFER on Line 3a (redline)    payor  64.5% / recipient  35.5%  -> funds $10,054/yr; order $1,206/wk vs $1,276 (saves $3,624/yr)
3.  POST-TRANSFER NET shares              payor  48.2% / recipient  51.8%  ($87,172 vs $93,821)  -> funds $7,513/yr
4.  POST-TRANSFER NET incl. child care    payor  48.2% (fixed point; equals rule 3)

Pre-transfer gross share (Line 3c basis, approx): payor  87.1%
Caveat that travels with every line: per person the payor still leads ($87,172 for one vs $23,455 each for four, rule 3).