Since it's been 3 weeks, a partial answer to explain the puzzle, without quite being able to spot the intended solution...
This puzzle has been inspired by another one on this site - namely, this one. The hints all point to this:
1. Check its URL - the puzzle can be found at node number 119698 on this very site (i.e. 'inside the house'). Since this puzzle clocks in at node number 119707, it can be found 'nine doors (i.e. nodes) down from this one'.
2. The creator of that puzzle is PSE user @Prim3numbah - a corruption of 'prime number', using a little 1337 (i.e. 'leetspeak' - here with the use of a '3' in place of an 'e') and 'a bit gangstah' in the use of the 'ah' ending in place of 'er'.
Now that puzzle revolved around...
...the aspect ratios of national flags (i.e. the standard proportions of their width and height). And that's again what is involved here. The first part of each row in the puzzle (before the slash) is one of these ratios.
There's another useful clue in the title too...
There are two capitalised letters in it - 'E' and 'U'. This means we are likely to need to think about European flags in particular.
And this is confirmed by an observation from the first line:
There are only two national flags whose standard aspect ratio is 1:1.4 (or 5:7) - Albania and Kosovo, both European.
So what might the numbers after the slashes represent? Something that immediately springs to mind...
...on looking at these flags is the number of colours used in the flag's design.
The number after the slash is a '3', and the flag of Kosovo uses 3 colours:
(Albania's has just 2 colours, so this would differentiate between them...)
So what does each row represent? I would suggest the following:
1 : 1.4 / 3: Kosovo:
2 : 3 / 2 | 1 : 2 / 6: Two nations (either side of the bar). The first (before the bar) could be Austria, Greece, Turkey or Ukraine:
The second (after the bar) is Croatia:
2 : 3 / 2: Again, one of Austria, Greece, Turkey or Ukraine (presumably a different one):
1 : 2 / 3: Bosnia-Herzegovina, Hungary, Ireland, or the UK:
However, since I have not yet managed to disambiguate these, it is impossible to know what the intention for a 'fifth line' would be. One thing that may come into play here is...
...differing statuses of EU membership, especially since (famously on all 3 counts) Kosovo is currently an applicant, Turkey's application is the subject of a high-profile freeze right now, and the UK is the only nation to have actually left the union. However, I'm not seeing it just yet...