The way the text inside a TextBox
item is rendered depends on several things. The most important one is the output format - Image, PDF, HTML, CSV, etc. In what format you experience the mentioned problem? The second thing is its font - what font and size you have set for the the TextBox item; The third and also very important thing you should have in mind is the size of the item. Also any border or padding can shrink the area where the TextBox renders its content.
As far as Telerik Reporting is concerned one can specify any dimension in millimeters (mm), centimeters (cm), inches, points (pt) and picas (pc; 1 PostScript pica is 1/6 inch or 12 points) (ref. Telerik.Reporting.Drawing.UnitType
enumeration) and there is no unit as characters.
So having the above in mind, the only advice we can give you is to take a look at the accompanying examples and then by some trials and errors you have to find the best configuration for your TextBoxes.
I hope this information helps. Thank you.
All the best,
the Telerik team