The scenario I've reproduced this issue in was originally started in version 1.04b11.
According to their tooltips, the retirement stratagems are, if refused, supposed to reduce the target's seniority by 25% for Bronze Retirement, 50% for Silver Retirement and 75% for Golden Retirement. However, this is completely inconsistent with their actual effects.
When checking the target's personnel file before and after applying the strategem, I have yet to see any of the cards reduce a target's seniority by anywhere near the advertised percentage. However, the value for seniority loss displayed on the popup the game showns after applying the strategem tends to be heavily inflated, often above and beyond the percentage stated in the tooltip and greater than the target's actual original seniority score.
It appears the seniority of leaders targeted for Bronze Retirement sometimes actually increases instead of being reduced, in which case I have seen the popup report a seniority decrease of 0.