How can this be explained mathematically?

Only my HTML page and guessing is how I arrived at that conclusion.

 DEF vs. % Reduction

% Reduction	Minimum DEF
1%	4
2%	16
3%	36
4%	64
5%	100
6%	144
7%	196
8%	256
9%	324
10%	400
11%	484
12%	576
13%	676
14%	784
15%	900
16%	1024
17%	1156
18%	1296
19%	1444
20%	1600
21%	1764
22%	1936
23%	2116
24%	2304
25%	2500
26%	2704
27%	2916
28%	3136
29%	3364
30%	3600
31%	3844
32%	4096
33%	4356
34%	4624
35%	4900
36%	5184
37%	5476
38%	5776
39%	6084
40%	6400
41%	6724
42%	7056
43%	7396
44%	7744
45%	8100
46%	8464
47%	8836
48%	9216
49%	9604
50%	10000
51%	10404
52%	10816
53%	11236
54%	11664
55%	12100
56%	12544
57%	12996
58%	13456
59%	13924
60%	14400
61%	14884
62%	15376
63%	15876
64%	16384
65%	16900
66%	17424
67%	17956
68%	18496
69%	19044
70%	19600
71%	20164
72%	20736
73%	21316
74%	21904
75%	22500
76%	23104
77%	23716
78%	24336
79%	24964
80%	25600
81%	26244
82%	26896
83%	27556
84%	28224
85%	28900
86%	29584