Yoreh Deah 120:3 one who Toivels a vessel should make the Bracha "Al Tevilas Keli". However if one Toivels two or more vessels they should make the Bracha "Al Tevilas Keilim". Aruch HaShulchan Yoreh Deah 120:22 disagrees and says one should always say "Al Tevilas Keilim" even if they are only Toveiling one vessel.
To the best of my knowledge I do not know of any other Bracha that we change based on the amount being done. For example, if one affixes one Mezuza or two Mezuzas the Bracha remains the same, "Likboha Mezuza".
Why would the Shulchan Aruch differentiate by Tevilas Keilim from all other instances where the Nusach of the Bracha remains the same regardless of the amount done?
