If 2023 was your first year, the base year would be 2022 and full-time equivalents would be zero.
According to the State of California:
The base year is the year before the 1st qualified employee is hired. The base year is taxable year 2020 for an employer who hired its first qualified full-time employee during taxable year 2021.
Once the base year is established, it does not change from year to year.
An employer must determine their annual full-time equivalents for their base year, and for each taxable year for which they will claim a credit. The number of full-time equivalents is the number of full-time employees who work the entire year and a pro-rata fraction for full-time employees who did not work the entire year. For full-time employees who worked part of the year, the fraction is determined as follows:
Part time employees are not included in the calculation of annual full- time equivalents."