How specify the step output chart?

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C#

Hello! I use chart control windows form.

private void Graphic(string valuta)
        {
            if (valuta == "EUR") { TST = EUR; } else if (valuta == "USD") { TST = USD; } else if (valuta == "RUB") { TST = RUB; } else { TST = RON; }

            Series set1 = new Series();

            for (int i = 0; i < days; i++)
            {
                set1.Points.AddY(TST[i]);
            }
            set1.BorderWidth = 2;
            set1.BorderDashStyle = ChartDashStyle.Solid;
            set1.ChartType = SeriesChartType.FastLine;
            set1.Color = Color.Green;
            GraphValutar.Series.Add(set1);
            GraphValutar.Invalidate();

        }

But values TST[i] are veru small, so the graph is obtained almost as a straight line.
How i can set step for output chart?