The TDA Rules and Recommended Procedures are meant to facilitate orderly games that are friendly, accurate, and timely.
Rule #49, in part, says: "It is the caller’s responsibility to determine the correct amount of an opponent’s bet before calling, regardless of what is stated by others."
It recognizes that others, including the dealer, might attempt to help the caller with information that may or may not be accurate.
Recommended Procedure #12 encourages dealers to announce the bet as action proceeds around the table. Clearly, the intent is to facilitate accurate game play.
Your question asks whether or not it is acceptable for a dealer to help the caller determine the amount required to call versus simply stating the total bet amount, thus leaving the required math exercise to the caller. As you note, some of your clients think that the dealer shouldn't help with the math.
That seems a bit silly to me. Do these clients think that an accurate and timely amount to call is some sort of arcane secret advantage not to be freely shared?