Use Series.Marks.DisplayFormat := '%.1f' for 1 decimal (or '%.1g' for AT MOST 1 decimal).
ok that was of course helpful but works only if i specify marks.style := smsCustom
if I put marks.style := smspercent, it seems that marks.style does not count as 2 decimal places get displayed every time
but let me tell you where was the problem. on some other chart, where i have more space, I used
a string that I found in some demo
Marks.Format := '%1:.2f%';
Marks.Style := smsPercent;
where left axis shows the numerus (which is preferable)
now I changed some charts that are very space restricted with your suggestion
Marks.Format := '%.1f%%'; // these %% are my addition because I want to show % sign
and now the y-axis shows percentage, as now I add percentages to the chart in order to display marks as I wish
the whole thing works well enough now (though I would prefer y-axis to show numerus, it is just odd that you cannot change the format the string when smsPercent is chosen
thanks!