Why do I need to indicate how much is for RMD on each individual IRA 1099-r distributions as long as my total distributions are over the total RMD required?

I have several individual distributions over several different IRAs. Some IRAs I took much more than required for that IRA, but others I didn't take any distributions.  The overall total  distribution was more than the total required, but don't know how to specifically put an RMD total for each individual distribution.