I do not quite understand what you are trying to do, it looks like you want to increment every second but using a timer like that will increment it every scan for 1 second so if the scan time was 20ms the value would change by 50 every second, in my post, Increment bit is the one that needs to be true so that every second the analog output is incremented by 10%, the decrement bit does the opposite, you just need to create the ladder in twido, then when you want the valve to open turn on the Increment bit or when you want to close it turn on the decrement bit. in other words my variables you need to use %xx.xx
You will need to set your own limits i.e. when decrementing the compare on mine is 0, however, if you only want it to go to 10% then just compare for > 10, depending on the type of analogue card you have the maths will need to be changed so if the maximum output of the analogue is 1024 then it is 1024 divided by 100 = 10.24, for analogue cards that require 2047 then it is 20.47
for 4096 it is 40.96 to convert it from 0-100% to the max raw value.
Sorry I cannot be more help as I do not have modicon software.