Question on step reward

[condorman]

Hi, I have a doubt about the reward function.
If in a specific state I get the action to close a LONG position, why do I calculate the reward starting from the closing of the next candle instead of the current one in which the action was indicated?

in code: trading_env.py

def step(self, action):
self._truncated = False
self._current_tick += 1

    if self._current_tick == self._end_tick:
        self._truncated = True

    step_reward = self._calculate_reward(action)
    self._total_reward += step_reward

why increase self._current_tick += 1 before reward?
shouldn't I reward him with the closing value of the candle in which this action was decided?

thank you!