the alpha value is not correct after compression by tct mac v4.2

hi guys, i just find the alpha value become much smaller after compression by Mali GPU Texture Compression Tool v4.2 mac version, this problem also happens in the latest version v4.3, but it works well in windows version, is it a valid issue? will it be fixed in the future version? thanks.

i guess the alpha value has been squared. 26/255 = 0.10196, 90/255 = 0.32594, 0.32*0.32=0.1024