With the salary conversion for a JobRad, you decide to receive a portion of your monthly salary not in cash, but as a non-cash benefit for the duration of the JobRad transfer. The salary conversion (the monthly leasing installments) from your gross salary reduces the base for the calculation of taxes and social security contributions.
Therefore, your employer will withhold the monthly leasing rate (conversion rate) from your salary and adjust the net salary payout accordingly.
For more information, you can find the JobRad FAQ at: https://www.jobrad.org/faq.html