Blanden trail running 15,4k

Blanden bosloop 15,4km
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goal time: 1h15
official time: 1h09'54''

avg hr: 165
peak hr: 181
cals: 1288

split times:

1) 5:03:69 (-) (150)
2) 4:43:46 (9:47:15) (166)
3) 4:44:16 (14:31:31) (158)
4) 4:35:56 (19:06:87) (160)
5) 4:35:09 (23:41:96) (155)
6) 4:54:91 (28:36:87) (168)
7) 4:31:85 (33:08:72) (163)
7,5) 2:48:78 (35:57:50) (161)
8,5) 4:51:38 (40:48:88) (169)
9,5) 4:39:72 (45:28:60) (171)
10,5) 4:32:33 (50:00:93) (166)
11,5) 4:24:68 (54:25:61) (167)
12,5) 4:14:33 (58:39:94) (165)
13,5) 4:35:18 (1:03:15) (176)
14,5) 4:05:69 (1:07:20) (175)
15) 2:28:37 (1:09:49) (176)

I don't know about how they measured the course, but on the official results it says 15,4km, 1h09:54, avg spd 13,2 km/h, which is correct.
On the course however, it's like the course fits perfectly, so my guess is that the last half km is actually a little longer then 1 km, because I was running pretty even splits, and I made an all out sprint the last 500 m, so it's hard to believe that it's only 500m, compared to my other splits where I was just running tempo.