To determine to what extent TenneT Holding B.V. should utilize hybrid bonds relative to S&P Global Ratings' cap, we must first calculate the current proportion of hybrid capital relative to the total adjusted capital (Debt + Equity) as of the end of 2022 (2023-01-01).

1.  **Calculate Total Debt**:
    Debt consists of long-term and short-term borrowings.
    Long-term Borrowings = 19,006,000,000 EUR
    Short-term Borrowings = 709,000,000 EUR
    Total Debt = 19,006,000,000 + 709,000,000 = 19,715,000,000 EUR

2.  **Calculate Total Equity**:
    Total Equity (including noncontrolling interests) = 7,713,000,000 EUR

3.  **Calculate Total Adjusted Capital**:
    Total Adjusted Capital = Total Debt + Total Equity
    Total Adjusted Capital = 19,715,000,000 + 7,713,000,000 = 27,428,000,000 EUR

4.  **Determine the S&P Cap**:
    S&P limits equity credit on hybrids to a maximum of 15% of total adjusted capital.
    S&P Maximum Hybrid Cap = 15% of 27,428,000,000 EUR = 4,114,200,000 EUR

5.  **Calculate Current Hybrid Capital**:
    The balance sheet shows Hybrid Capital of 2,125,000,000 EUR.

6.  **Calculate Utilization Extent**:
    Extent = Current Hybrid Capital / S&P Maximum Hybrid Cap
    Extent = 2,125,000,000 / 4,114,200,000 ≈ 0.5165 or 51.65%

Rounding to the nearest provided option, the utilization extent is approximately 50%. The company has already utilized about half of the maximum capacity allowed by S&P Global Ratings' cap for equity credit on hybrids.

<answer>50%</answer>