Fast vs Slow advertising, where is the border between?

[Valer_I]

Hello all, I am trying to adjust the current consumption of my device based on nrf51822 s130. A have read the https://developer.apple.com/hardwaredrivers/BluetoothDesignGuidelines.pdf recomendations and want to follow them. In code I found struct ble_adv_modes_config_t

bool     ble_adv_fast_enabled;      /**< Enable or disable fast advertising mode. */
uint32_t ble_adv_fast_interval;     /**< Advertising interval for fast advertising. */
uint32_t ble_adv_fast_timeout;      /**< Time-out (in seconds) for fast advertising. */
bool     ble_adv_slow_enabled;      /**< Enable or disable slow advertising mode. */
uint32_t ble_adv_slow_interval;     /**< Advertising interval for slow advertising. */
uint32_t ble_adv_slow_timeout;      /**< Time-out (in seconds) for slow advertising. */

It seems that both fast and slow could be configured at init and it should be the trigger that switches between fast and slow. Am I correct? Otherwice it hard to imagine cases like :

  ble_adv_fast_enabled == true;   //& 
  ble_adv_slow_enabled == true; 

So I have two time windows for fast and slow advertising ( 20ms @ 30s and 1285ms@10min) the timeouts could be catched in BLE_GAP_EVT_TIMEOUT event

 if(ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_ADVERTISING){ ... }

Please direct me to sample code or explain how to configure and switch advertisement modes in the most proper way.

sincerely yours,