In the challenge for the "Using Formula Fields" Trailhead module, I'm using the formula, TODAY()  -  LastModifiedDate, with the type set as Number (as specified in the challenge instructions, but I receive the following syntax  error: Error: Incorrect parameter type for operator '-'. Expected Number, Date, received DateTime.

I am a total admin n00b and would appreciate any feedback on the (probably obvious) element I'm missing here. Thanks!

In the challenge for the "Using Formula Fields" Trailhead module, I'm using the formula, TODAY()  -  LastModifiedDate, with the type set as Number (as specified in the challenge instructions, but I receive the following syntax  error: Error: Incorrect parameter type for operator '-'. Expected Number, Date, received DateTime.

I am a total admin n00b and would appreciate any feedback on the (probably obvious) element I'm missing here. Thanks!