@Forum-team , I kindly ask that you escalate this issue to the product team to have a look - this one is definitely in the ānot expected behaviourā category 
Not sure whether the introduction of (the very useful) formatting feature within formulas has caused this to break, or it was always the case but I will try and explain as best as possible in order for you to recreate, test, and hopefully fix since the use cases are numerous! 
One use case is to set a single-select field called āStatusā to display whether a task/milestone is āOn trackā or āOff trackā, based on whether the taskās due date has shifted compared to itās ābaselineā (a date field). This rule would leverage a formula field called āVarianceā that would look like this, giving us an output in ādaysā.
Below is the rule using the āNumber isā condition to simply change the single-select fieldās options. Looks fine, right? Well it doesnāt run at all 
However, the rule runs perfectly fine when I replace the formula field with a simple number field. So my hunch is that there is something not working correctly with formula fields.
I think the problem is in the way my āVarianceā formula field is written - it basically converts the native weeks/days output into minutes (by using the +0) and then divides the minutes within a day (1,440) to get the output in days, formatted as such (which I donāt think is the problem):
Call this a hacked formula?
Side note, the API reveals that the values of the formula field are whole numbers and nothing strange between the display value and number value.
Iāve noticed that if you create such as formula (which includes dates) but without applying the formatting immediately (before you hit āCreate fieldā) then you will not be able to format it later. This is what you see if you try to format later, or if you try and format a simple Due date - Today formula upon creation:
Note, such formulas are not available in a Ruleās āNumber isā condition. So at this point, Iām thinking perhaps Iāve done something Asana does not want me to - Iāve made a āhackedā formula (that contains date fields), available to be used in the āNumber isā condition of a rule. But my argument is, since Asana lets me format the formula into a ānumber of daysā value, then why not let me use this number in the check if āNumber isā condition in the rule?
It would be awesome if it could! Please donāt tell me this is expected behaviour
Further testing:
I even tried to place the āVarianceā formula into another formula and instead use that in the rule, but neither that worked with the rule.
I also tried a simple formula field with a fixed number as per below - the rule triggered correctly each time I changed the formula, concluding that it is not formula fields in general, only my particular āhackedā formula:
I started getting somewhere when I tried adding more āWhensā and changed the conditions to include an āotherwiseā instead and this actually worked, but only once, when the variance value was initially set/populated. After the variance field (and status field) was set, the rule did not seem to run again.
And strangely enough, the above rule worked perfectly when the āBaseline dateā (date field) was changed (but not when the Due date field is changed). So is there something wrong with the due date updating the formula fieldās value or triggering the rule?!
Something is definitely not right
Ideal solve:
Clearly, this would all be solved if I didnāt need to create this āhackedā formula field and instead Asana would allow formatting of formulas that contain any date related fields, including created on, today, etc. so that they can be used in the āNumber isā condition of rules.
