How to create filter in alert composer?

Summary:

When creating a filter with alert composer I receive this error:

The filter expression is invalid. The error message is: TRUNC(${withdrawnDate}) >= ${AlertFilterUtils.addDays(learningItemEffectiveDate,-2)}. (HRC-1035496)

Content (required):

We don't want learners to cancel course enrollment if course start date is less than 2 days. Since we didn't find a way to do that, we want at least to notify them by using alert composer. We tried the following approach but for some reason it returns error:

The syntax seems to be correct and we don't understand why it isn't accepted.

Version (include the version you are using, if applicable):