Very simple generic increment/decremental list

IncList.cs

    public class IncList<T>
    {
        private readonly IDictionary<T,int> _incList;

        public IncList()
        {
            _incList = new Dictionary<T, int>();
        }

        public void Add(T item)
        {
           AlterCount(Movement.Inc,item);
        }

        public void Dec(T item)
        {
            AlterCount(Movement.Dec,item);
        }

        public int Get(T item) => _incList[item];

        public void Delete(T item)
        {
            _incList.Remove(item);
        }

        public int Total => _incList.Count;

        public bool Exists(T item) => _incList.ContainsKey(item);
        
        private void AlterCount(Movement movement, T item)
        {
            if (!Exists(item))
            {
                _incList.Add(item,0);
            }
            
            if (movement == Movement.Inc)
            {
                    
                _incList[item] += 1;
            }
            else
            {
                _incList[item] -= 1;
                if (_incList[item] < 0)
                    _incList[item] = 0;
            }
        }

        private enum Movement
        {
            Inc,
            Dec
        }
    }