The graphs don’t depict numbers, but they depict percentages.
If there are only 40 homosexual couples in Mississippi, then 10 of them have children.
There might be 10,000 homosexual couples in California, with 20%, 2000 having children.
Really can’t imply much from the stats on exact numbers.
It doesn’t appear to me that the Census Bureau actually tracks this sort of information.
My guess as to what’s going on: Mississippi has a larger percentage of single-parent families, and this outfit “estimated” how many were gay.
2011 ACS:
CA
MHH: 748432 56.5% with children under 18
FHH: 1710901 64% with children under 18
NHH: 3950225 0.8% with children under 18
0.7% overall with same sex unmarried partner.
MHH: 50001 54.6% with children under 18
FHH: 203448 68% with children under 18
NHH: 340033 0.9% with children under 18
0.3% overall with same sex unmarried partner
But no, they do not break out the 0.7%/0.3% across categories so there is no way to know, by census data alone, how many gays have children.
MHH = male head of household, FHH = female head of household, NHH = nonfamily household.