Based on the financial facts and market data provided for Fortum Oyj for the fiscal year ended December 31, 2022, the company should be advised to issue 0% of its total adjusted capital in hybrid bonds. 

Here is the reasoning:
1. **Historical Hybrid Issuance:** Fortum Oyj has never issued hybrid bonds, and specifically did not do so in 2021 or 2022. As indicated in the guidelines, an entity's lack of prior hybrid bond issuance is a highly reliable signal that there is little strategic intent or financial necessity to introduce this instrument into its capital structure in the near future.
2. **Strong Credit Metrics:** The company's leverage metrics indicate a very healthy balance sheet. With an S&P Net Debt / EBITDA ratio of 1.84x and an S&P FFO / Net Debt ratio of 45.56%, Fortum exhibits robust debt protection and cash flow generation capacity for a utility. 
3. **Improving Leverage Profile:** Moody's adjusted leverage trend for 2022 is marked as "Improving," indicating limited to no deterioration in its credit metrics. The company does not face significant leverage pressure that would necessitate the equity credit from hybrid bonds to defend its investment-grade rating.
4. **Cost of Debt vs. Hybrid Issuance:** In an environment of rising swap rates and higher yields (as seen in the 2022 swap curve and the corporate bond indices), introducing a sub-senior debt instrument would likely materially increase the overall cost of capital without providing a necessary rating benefit, given the existing substantial rating headroom. 

Because the company has no current hybrids in its capital structure, maintains strong credit metrics, and requires no urgent structural leverage optimization to protect its rating profile, issuing hybrid bonds is not recommended.

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