If you think the text is less important than the window size (which your description seems to suggest),
Actually, the start of this discussion was the feedback of LordAro, that the width of the window is far too big. So I tried to make it smaller.
But you are right, the default should be that all the text is visible.
perhaps the string shouldn't be so prominently visible. Guis don't tend to explain relations between the fields with a long string of text.
Excel doesn't have text explaining how one cell relates to another cell, or we don't explain in text that you need to setup the newgrf settings in the main menu before you press new-game.
Ok, then lets have a look at it in detail:
Version until yesterday: "Timetable start 1. Jan 1905 + Vehicle Offset 1 month = Vehicle start 1. Feb 1905 Timetable length 2 months"
Version now: "Timetable start 1. Jan 1905 + Offset 1 month = Vehicle start 1. Feb 1905 Length 2 months"
The relations I use for explaining are just the math operators "+" and "=", so IMHO they are not a big problem, the space they occupy is quite small. And if I would omit them, I would need to add some space between the different labels anyway.
Maybe, however, I could distribute things among those two lines in a different way, e.g.
First line: Timetable start 1. Jan 1905 Length 2 months Name R17
Second line: Vehicle start 1. Feb 1905 Offset 1 month <Autofill information if autofill is active>
(where an active autofill might increase the space somewhat (though less than currently implemented), but as an active autofill is a quite seldom case that temporary width increase might be more acceptable)
If you feel you must explain it, perhaps
1. A tooltip somewhere explaining the relation
2. A "help" window (or area), like the settings window
3. A wiki page explaining time table in full detail (much more space than you could ever do in-game)
Actually, at least (1) and (3) are needed anyway; (2) possible maybe in a separate window; for a separate area carrying static text, I probably don't have the space in that window. But I personally would give (1) and (3) priority.
My hope is / was just, that if I am able to present the information in that window understandable enough, I might be able to reduce the need to read that more extensive information significantly. I mean, IMHO, tooltips or external information is good, but if a GUI makes you understand how things work without the need to read that information, it is even better.