I ran a half marathon yesterday, but my split times look strange (feat. Run Seoul Run)

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These are the official records and the records measured via the Nike app.
The official records
were measured by dividing the segments into 3, 9, 15.5, and 21.1:
0~3 : 551
3~9 : 539
9~15: 509
15~21: 550
It comes out like this.
If I recalculate the Nike app records using those same segments:
0~3 : 537 (- 14)
3~9 : 534 (- 5)
9~15: 529 (+20)
15~21: 539 ( - 11)
It comes out like this.
The official record shows a 509 pace for the 9~15.5 segment,
but honestly, I have never run at a 509 pace for 6km, nor do I have the ability to do so.
I could maintain it for about 1km, but 6km at that speed during a half marathon??
That is beyond my capability lol
Before the start,
I planned to increase my pace from 550 => 540 ==> 530
with the goal of finishing under 2 hours,
but my pace was around 535 in the beginning, so I hesitated for a bit but just kept running.
It is also true that my pace dropped after 16km.
I was almost ready to give up during the last 2~3km.
Anyway, the fact that the pace came out like that
means the actual measurement locations were wrong,
which would mean other people's results should look like that too...
Is it like that for everyone???
Even looking at it myself, it seems a bit strange.