If you use the below - r is not passing the valid state
$("#spreadsheet").kendoSpreadsheet();
var spreadsheet = $("#spreadsheet").data("kendoSpreadsheet");
var sheet = spreadsheet.activeSheet();
sheet.range("A1").value("r");
sheet.range("A1").validation({
from: "r",
comparerType: "equalTo",
dataType: "text",
messageTemplate: "Not Valid."
});