Why doesn't ModelState.IsValid become False even though Remote returns false?

Question

ASP.NET

Why doesn't ModelState.IsValid become false even though Remote returns false?
Is the check done for enough money in the account for the transaction?
Model:

[Required(ErrorMessage = "Введите сумму ставки")]
        [Range(MinBetSum, MaxBetSum, ErrorMessage = "Сумма от 50 до 50000")]
        [Remote(action: "InCash", controller: "Validate", ErrorMessage = "Недостаточно средств")]
        public decimal Sum{ get; set; }

Validation in controller: Validator:
ModelState.IsValid == false

[AcceptVerbs("Get")]
        public async Task<JsonResult> InCash(decimal Sum)
        {
            User user = await db.Users.FirstOrDefaultAsync(u => u.Username == User.Identity.Name);
            bool res = user.Balance >= Sum;

            return Json(res);
        }