what was the maximum percentage gain spy reached between september 2019 and september 2020

Between September 1, 2019 and September 30, 2020, SPY returned 18% and Gladstone Investment (GAIN) returned -13.9%.

DATEGladstone Investment
September 30 2020
$311.28
$5.11
September 29 2020
$308.94
$5.17
September 28 2020
$310.63
$5.26
September 25 2020
$305.55
$5.09
September 24 2020
$300.69
$5.01
September 23 2020
$299.89
$5.04
September 22 2020
$307.01
$5.16
September 21 2020
$303.92
$5.14
September 18 2020
$307.34
$5.18
September 17 2020
$310.92
$5.18
September 16 2020
$313.68
$5.13
September 15 2020
$314.93
$5.14
September 14 2020
$313.34
$5.16
September 11 2020
$309.27
$5.11
September 10 2020
$309.11
$5.12
September 09 2020
$314.58
$5.19
September 08 2020
$308.48
$5.18
September 04 2020
$317.15
$5.14
September 03 2020
$319.76
$5.18
September 02 2020
$331.16
$5.25
September 01 2020
$326.43
$5.24
August 31 2020
$323.39
$5.23
August 28 2020
$324.56
$5.23
August 27 2020
$322.48
$5.19
August 26 2020
$321.78
$5.18