Maintenance percents not shown

[Carlosgrr]

Version of OpenTTD

Tested on 1.10.3, but this is a really old problem.

Steps to reproduce

Select "Settings" in the start menu, change "Category" to "Expert". After that open the "Company" option and change the option "Maintenance intervals are in percents": to "On".

Actual result

The "Default maintenance interval for ..." options display: 50 days/%
This implies that the trains will be doing maintenance for 50 days for each maintenance percent lost and not what it is currently being used for, this is a major problem in the UI since many players have had problems understanding these settings without any external help.

Expected result

The options for "Default maintenance interval for ..." all vehicles should display:
50%
or
50% of max engine reliability

And once the user clicked the option it should display a better descriptive text with an example, like this:
Set the reliability drop necessary to send a train for maintenance.
Example Train A - Max Engine Reliability: 90% || Current Value: 20%
20% of 90% = 18%
Hence the train will go to maintenance at 72% (90% - 18%) reliability).