Ranged Formula tool issue

[Madzy]

Hey I am having an issue with my formula tool regarding on doing a ranged formula. 

IF [Days] >= "0" AND [Days] < "30" THEN
"0 - 30 Days"
elseif [Days] >= "30" AND [Days] < "60" THEN
"30 - 60 Days"
elseif [Days] >= "60" AND [Days] < "90" THEN
"60 - 90 Days"
elseif [Days] >= "90" THEN
"Greater 90 Days"
else Null()
endif

This is y formula but it is spouting out 

Where I want those to be > 90 days. Any suggestions? 

BTW The days columns is being generated by a formula --> DateTimeDiff(DateTimeToday(),[Invoice Date],'days')

[DataNath · Accepted solution]

Hey @Madzy, the issue here lies with using the wrong data types. When making your [Days] field, make sure it's numeric (options in the dropdown):

Then, for your [>= Days] field, write this without the quotes around the numbers:

IF [Days] >= 0 AND [Days] < 30 THEN
"0 - 30 Days"
elseif [Days] >= 30 AND [Days] < 60 THEN
"30 - 60 Days"
elseif [Days] >= 60 AND [Days] < 90 THEN
"60 - 90 Days"
elseif [Days] >= 90 THEN
"Greater 90 Days"
else Null()
endif