So one time I go to Mass in New York and when entering the church there was a table with two bowls. There was a sign that said, “If you are going to receive communion today, please take a wafer from this bowl and put it in the other bowl.”
First of all: Ew.
Secondly, it was a valiant effort to fulfill paragraph 85 of the GIRM. This paragraph points out that the priest is BOUND to receive a host that was consecrated at the Mass being celebrated. (That is, not taken out of the tabernacle from that which was consecrated at another Mass.) It is “most desirable” (pretty strong wording without making it mandatory) that the whole congregation (as you were anointed prophets, kings, and priests after all) also receive hosts consecrated at the Mass being celebrated.
This is trickier than you might think. You people are not all that predictable. A former liturgist for the Diocese of Cleveland CLAIMED that this should be no problem and that he would be able to do it at any parish in the diocese. Perhaps he was clairvoyant and so I bow to his super powers. We are not so talented (though we have improved mightily.)
Anything can throw the numbers off at Mass. A football game. A holiday. Nice weather. Bad weather. The grass mowed in the wrong direction. The numbers become thrown off because of people coming late because of roadwork, last minute soiled diapers, having to park three blocks away, trying to catch the end of “Jason and the Argonauts.”
So you try to cut it close and then your are left with having to break the last remaining host into micro-particles in order to have enough for everybody to receive communion. The next week you have “learned your lesson” and put out extra (better to be caught with a little extra than not enough right) and then you find, at the end off Mass, that you won’t have to consecrate again for the next month.
Sacristans debate in angst before Mass about how much to put out especially at funerals. “Do you think I should put out more? Will there be a lot of people at this funeral? How many people were at calling hours?” My standard answer, which they have not caught on to after 8 years, is “I don’t know.”
So you do your best. Sometimes you do well, sometimes not so much.
This paragraph also states that Communion under both species be offered whenever it is feasible, not open to profanation, and suitable as determined by the priest under the guidelines of the local council of bishops.
Here is another area of difficulty. How much wine should we prepare to be consecrated? Some weeks we run out. Some weeks the deacon consumes so much that I worry about him walking down the aisle.
Eh. If this is our biggest problem, we are doing pretty well.