Why is the diff changing every couple of minutes?

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 GPU 0:  53.0C 1492RPM | 8.944M/8.923Mh/s | R:0.4% HW:0 WU:0.0/m T:1 I: 8
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 [23:04:52] Accepted 208f5fd2 Diff 0/0 GPU 0 at Pool 0
 [23:05:04] Accepted 30320728 Diff 0/0 GPU 0 at Pool 0
 [23:05:14] Accepted 011ed9d7 Diff 1/0 GPU 0 at Pool 0
 [23:05:18] Pool 0 difficulty changed to 0.017357
 [23:05:25] Accepted 1ad07e61 Diff 0/0 GPU 0 at Pool 0
 [23:05:29] Accepted 20404488 Diff 0/0 GPU 0 at Pool 0
 [23:05:50] Accepted 150a3893 Diff 0/0 GPU 0 at Pool 0
 [23:05:51] Accepted 2f8bc6f1 Diff 0/0 GPU 0 at Pool 0
 [23:05:58] Accepted 322aab06 Diff 0/0 GPU 0 at Pool 0
 [23:06:00] Accepted 27766b23 Diff 0/0 GPU 0 at Pool 0
 [23:06:05] Accepted 2abb1749 Diff 0/0 GPU 0 at Pool 0
 [23:06:15] Accepted 32e8e057 Diff 0/0 GPU 0 at Pool 0
 [23:06:20] Accepted 2b5436d6 Diff 0/0 GPU 0 at Pool 0
 [23:06:24] Accepted 02a81753 Diff 0/0 GPU 0 at Pool 0
 [23:06:32] Accepted 13118262 Diff 0/0 GPU 0 at Pool 0
 [23:06:54] Accepted 26d38c9f Diff 0/0 GPU 0 at Pool 0
 [23:06:57] Accepted 287170c2 Diff 0/0 GPU 0 at Pool 0
 [23:07:10] Pool 0 difficulty changed to 0.020250
 [23:07:31] Accepted 0ca41c85 Diff 0/0 GPU 0 at Pool 0
 [23:07:44] Accepted 22c58893 Diff 0/0 GPU 0 at Pool 0
 [23:07:49] Accepted 2757a7e3 Diff 0/0 GPU 0 at Pool 0
 [23:07:51] Accepted 19430dd4 Diff 0/0 GPU 0 at Pool 0
 [23:07:51] Accepted 1e313454 Diff 0/0 GPU 0 at Pool 0
 [23:07:52] Accepted 2ad0d216 Diff 0/0 GPU 0 at Pool 0
 [23:08:08] Accepted 9ed8af2f Diff 2/0 GPU 0 at Pool 0
 [23:08:12] Accepted 2dacd2ff Diff 0/0 GPU 0 at Pool 0
 [23:08:16] Accepted f972d3ae Diff 1/0 GPU 0 at Pool 0
 [23:08:19] Accepted 2d915e03 Diff 0/0 GPU 0 at Pool 0
 [23:08:35] Accepted 2be8eaee Diff 0/0 GPU 0 at Pool 0
 [23:09:09] Accepted 2dcca49b Diff 0/0 GPU 0 at Pool 0
 [23:09:20] Accepted 26742c54 Diff 0/0 GPU 0 at Pool 0
 [23:09:30] Accepted 0a706b7b Diff 0/0 GPU 0 at Pool 0
 [23:09:34] Pool 0 difficulty changed to 0.019677
 [23:09:50] Accepted 19f9bb22 Diff 0/0 GPU 0 at Pool 0
 [23:09:52] Accepted 09f92e23 Diff 0/0 GPU 0 at Pool 0
 [23:09:55] Accepted 056ef5f8 Diff 0/0 GPU 0 at Pool 0
 [23:09:56] Accepted 187ac73c Diff 0/0 GPU 0 at Pool 0
 [23:10:10] Accepted 290a2109 Diff 0/0 GPU 0 at Pool 0
 [23:10:18] Accepted 2c6cab31 Diff 0/0 GPU 0 at Pool 0
 [23:10:20] Accepted 306ef66c Diff 0/0 GPU 0 at Pool 0