Congratulations on your curiosity. It is just such searching that does reveal the sensus plenior of Scripture hidden in pattern and riddle.
There are several patterns which do have meaning. This one relates to things words used on each day.
The last three days mirror the first three. Each day is like a table of contents entry to the rest of the Bible and each speaks of the hidden picture of Christ within each portion.
The last A points to the first A to close the chapter. It extends into verse 2.5 to clarify which reference to heaven and earth it is referring to; the one before the plants and herb: so not (a) but (A). This eliminates the invented contradiction of the wrong order of creation.
The 3 + 3 pattern is reflected in 1John 5:7,8 which gives the key to unlocking the pattern in Ge 1. the first three days are 'heavenly testimonies' the second three are 'earthly' testimonies.
It is easy to say a pattern is an important pattern when: 1. it reveals Christ in agreement with the literal revelation in the NT. 2. The metaphor within is consistent with teh metaphor every where else. 3. The metaphor is derived from the metaphor within the words themselves. 4. the pattern is validated other places (2 or 3 witnesses).
Sensus plenior is not as free-wheeling as people presume it to be.
It is nearly impossible to say that what you are observing is not sensus plenior, but we can say that we don't see it yet.
Though the NT authors do occasionally use numbers, their meanings are well-established and not subject to free-for-all.
2 relates to the Biblical dualism of Holiness and Love
3 relates to the Trinity
4 to the four voices of God through prophets, priests, kings and judges.
If your number patterns are meaningful, they will either agree with these, or present an alternative meaning that replaces these everywhere they exist. Such is the nature of intellectual humility in sensus plenior. We recognize that not all riddles have been solved, and until they are solved, we do not have a complete picture, just an improving one.
Another important pattern is when there is a pattern established and then broken. the break in the pattern has meaning. All days were good but one. This day is a prophecy of the great and terrible Day of the Lord. It was not a good day. Can you discern why?