The example provided is from the section your reference. The full text is below:
• If you are not treated as having family coverage for each
month, use the following steps to determine the amount to
enter on line 6.
Step 1. Refigure the contribution limit that would have
been entered on line 5 if you had entered on line 3 the total of
the worksheet amounts only for the months you were treated
as having family coverage. When refiguring line 5, use the
same amount you previously entered on line 4.
Step 2. Divide the refigured contribution limit from Step 1
equally between you and your spouse, unless you both agree
on a different allocation (such as allocating nothing to one
spouse).
Step 3. Subtract the part of the contribution limit allocated
to your spouse in Step 2 from the amount determined in Step
1.
Step 4. Determine any other contribution limits that apply
for the tax year and add that amount to the result in Step 3.
Enter the total on line 6.
Example. In 2023, you are an eligible individual and have
family HDHP coverage. In March, you divorce and change
your coverage as of April 1 to self-only. Neither you nor your
ex-spouse qualify for the additional contribution amount. Your
ex-spouse continued to have family HDHP coverage and was
an eligible individual for the entire year. The contribution limit
for the 3 months you both were considered to have family
coverage is $1,937.50 ($7,750 × 3 ÷ 12). You and your
ex-spouse decide to divide the family coverage contribution
in the following manner: 75% to your ex-spouse and 25% to
you. Your contribution limit for 9 months of self-only coverage
is $2,887.50 ($3,850 × 9 ÷ 12). This amount is not divided
between you and your spouse.
Because you are covered under a self-only policy on
December 1, you will show $3,850 on line 6 (the greater of
either (a) $3,371.87 ($1,937.50 family coverage + $2,887.50
self-only coverage – $1,453.13 spousal allocation) or (b) the
maximum amount that can be contributed ($3,850 for
self-only coverage)). Your ex-spouse would show $7,750 on
line 6 (the greater of either (a) $7,265.62 ($1,937.50 family
coverage for the 3 months prior to the divorce + $5,812.50
family coverage maintained after the divorce – $484.38
spousal allocation) or (b) the maximum amount that can be
contributed ($7,750 for family coverage)).
