The most likely explanation is:
The primary consumer took in 5,000 units of energy and released 4,950 units, leaving 50 units for the secondary consumer to take in.
In a typical energy transfer in an ecosystem, energy is lost at each trophic level due to metabolism, respiration, and other biological processes. Therefore, the primary consumer would only retain a small portion of the energy they consume from the producer, allowing the secondary consumer to get a fraction of that energy.