Hello Nguyen,

When I set up 100 meters for horizontal reduction , my project does not work.

I take a look to your provided coordinate files. Here, the UTM zone number is missing and, thus, the simple check of your coordinates failed, i.e.,

if (yS >= 1100000 && yS <= 59800000 && yE >= 1100000 && yE <= 59800000) {
  // do reduction
}

kind regards
Micha