The punchline is that the numbers agree and the concepts do not. If you got the same two ratios, you found it.
1 · The old way
Target capital used to include the margin, and the margin was then removed from both sides:
TC_old = 555 + 90 = 645
RBC_old = 980 (before deducting the margin)
ratio = (980 − 90) / (645 − 90) = 890 / 555 = 160.4%
2 · The current way
The margin is a liability, so it is deducted in arriving at risk-bearing capital, and target capital never contained it:
TC = 555
RBC = 980 − 90 = 890
ratio = 890 / 555 = 160.4%
3 · Why they agree
They are algebraically the same expression. Writing RBC_net = RBC_gross − MVM and TC_old = TC + MVM:
(RBC_gross − MVM) / (TC_old − MVM) = RBC_net / TC
The revision did not change the answer. It changed where the margin lives — from an adjustment applied to both sides of a ratio, to an ordinary liability on the balance sheet. That is why the ordinance could then state the ratio in one line, and why it is now directly comparable with solvency ratios elsewhere.
4 · Doubling the margin
With MVM = 180 and everything else unchanged:
old: TC_old = 555 + 180 = 735; (980 − 180) / (735 − 180) = 800 / 555 = 144.1%
new: RBC = 980 − 180 = 800; 800 / 555 = 144.1%
Both drop from 160.4% to 144.1% — again identically, for the same algebraic reason.
Which makes the effect easier to see? The current one. In the new form the margin moves one number, the numerator: a longer run-off costs you available capital, full stop. In the old form the same margin appeared twice, moving numerator and denominator together, and you had to do the algebra to convince yourself the effect was not partly self-cancelling.
What to notice
The trap in this drill was the phrase risk-bearing capital. The 980 is assets minus liabilities before the margin; the 890 is after. Feed 980 into the current formula and you get 176.6% — a filing that is wrong by 16 percentage points because two definitions were mixed. When you read someone else's SST figures, establish which side of the margin their RBC is on before you compare anything.