Bluenrg peripheral max bonded devices

[FLola.1]

Hello, we are developing a device with SPBTLE-1S starting from BLE_Security peripheral example. We choose bond initialization with fixed pin.

Everything is working, except the fact that we cannot bond more than 4 devices (smartphones android or apple). While the chip is running it can bond with more than 4 devices, but at restart only last 4 devices are left. In library we found that MAX_NUM_BONDED_DEVICES is 12, and debugging the flash at FLASH_SEC_DB_SIZE we found it is not full. Is there any definition or function to set the real limit of bonded devices?