Iowa Code § 49.64: Number of ballots delivered.

The commissioner shall cause ballots of the kind to be voted in each precinct to be delivered to the precinct election officials as follows:

1. In general elections which are presidential elections, at least fifty-five ballots for every fifty votes, or fraction of fifty votes, cast in the precinct at the last preceding general election which was also a presidential election.

2. In general elections which are not presidential elections, at least fifty-five ballots for every fifty votes, or fraction of fifty votes, cast at the last preceding general election which was not a presidential election.