In a presentation Tuesday to the Rotary Club of Indianapolis, Superintendent Lewis Ferebee told members that if they supported two referendums to increase funding for Indianapolis Public Schools, the property tax bill for the average home would go up by “about $4.36 a month.”

That number also appeared on his slide presentation. The website of Vote Yes for IPS, the political action committee supporting the referendums, also listed the average tax increase as $4.36 in answer to the question, “How much will the referendum cost me each month?”

The problem is, that figure is wrong. The anticipated bill is actually lower, and Ferebee and the PAC website were using an outdated tax rate.

It’s off by about $1 — but the mistake shows the confusion surrounding the district’s 8-month-long dance over how much to seek from voters.

For a home worth $75,300, the median value used by the district, the estimated monthly cost of both referendums is $3.19, according to an analysis for the district by consultant H.J. Umbaugh and Associates. That is also the total generated by the district impact calculator.

Robert Vane, the lead consultant for Vote Yes for IPS, said he accidentally used the wrong number on the website and in the presentation. “Don’t blame the district,” he added. “Blame me.”

The $4.36 amount is the projected cost using an outdated figure for the operating referendum that the Indianapolis Public Schools Board approved July 17 — but then changed. Just a week later, the board voted to lower the amount it was seeking to about $220 million over eight years. That’s about 19.6 cents per $100 assessed valuation per year.

The operating referendum would help raise money for costs like teacher salaries, while a second measure would pay for facility improvements.

The decision to lower the request for operating costs came after last-minute negotiations with the Indy Chamber. The deal with the chamber was the culmination of months of political back-and-forth in a referendum campaign. The amount the district was seeking had been lowered twice before, and the ballot measures were postponed from May to November.

But Vane said he does not expect the mistaken number to have a notable impact on the campaign.

“Let’s not please overplay it,” he said. “It’s an error.”