IFS Cloud lobby - Error with variable substitutions (DATES)

Hi, 

In designing lobbies in IFS Cloud we could use variable substitutions such as ‘#START_OF_THIS_WEEK#’. 
I encountered an issue when we use these variables in WHERE conditions with - (days). 

e.g. 

 if we have a criteria to take the date before the start of the week, I would think that this would work. 

‘#START_OF_THIS_WEEK#’ -1 

but we ended up here with the following error.

but, if we use the database method to retrieve the same value here. it works fine. 

Am I doing something wrong with the use of these substitution variables? or is this a bug? 

If we use the variables alone they works fine.