The amount of light beams on top of the pit are the amount of oportunities you have left. If you refill the light pit you will earn back another beam.
Unfortunally, if all beams are active and you interact with the light pit you won't gain another extra oportunity. This means 25 is your maximum.
There are two really important ligh pits worth mentioning: the one in the Sun and the other in the Icelands. Make sure to know their location, specially the on on The Sun to spend less time refilling oportunities.