What does “[Ljava.lang.Object;@” mean?

I am filling a Google spreadsheet from a form. The code writes some information into the spreadsheet, it always does it right, but before writing what it is supposed to, it writes [Ljava.lang.Object;@1c7aa4fc (or something like that) on the last row in the spreadsheet. Why is it appearing there?

The code for writing into the spreadsheet:

for (var p = 1; p < data.length; p++) {
    var ppopis = data[p][2]; 
    var sstav = data[p][7];
    var ukonceno_dne = data[p][9];
    var cell = spred2.getRange("H"+(p+1));
    var celll = spred2.getRange("J"+(p+1));
    if(nadpis_pole == ppopis && vlozena_hodnota == "Zrušeno") {
      cell.clear();
      cell.setValue("Zrušeno");
      if(ukonceno_dne == "" || ukonceno_dne == null){
        celll.setValue(dnesni_datum);
      }
    } else if (nadpis_pole == ppopis && vlozena_hodnota == "Vráceno") {
      cell.clear();
      cell.setValue("Vráceno");
      if(ukonceno_dne == "" || ukonceno_dne == null){
        celll.setValue(dnesni_datum);
      }
    }
  }

Thanks :)