Hello Kaliban
The solution to your problem is the to create an automatic calculation and then use the dynamic result as a variable in GoodTillTime.
Look at the example below:
The first block ads 30 minutes to the last candle time. a2*60*1000 is to convert 30 minutes in milliseconds.
Than we will create a new variable out of the output value.
In the pending order block, we simply drag and drop the variable created to the GoodTillTime section.
I hope that was clear enough. If not, do not hesitate to ask for more explainations.