Let's start with some math.

The coming "middle class tax-cut" is going to cost the government $600 million more than the Liberals had first thought.

The offsetting tax hike on Canada's richest "one per cent" is going to bring in $800 million less than the party had planned in its election platform.

According to the Finance Department's fiscal update, next year's budget balance is $4.5 billion lower than the Liberals planned on.

Still to come are updated numbers for many other election promises including: the Canada Child Benefit, infrastructure spending, and new money for jobs and training.

For what it's worth, those three promises alone were estimated in the Liberal platform to cost about $9 billion — which means they are likely cost … who knows?

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Minister of Finance Bill Morneau may be looking to cut some Liberal promises as he head toward next year's budget (Sean Kilpatrick/Canadian Press)

Add it all up, and before pen has hit paper on next year's budget, the Liberals look to be already in the hole by about $15-billion — 50 per cent more than the Liberal election platform promised either of the first two deficits would be.

Perhaps that's why, when pressed repeatedly on whether the promise to keep deficits below $10 billion was still on the table, Finance Minister Bill Morneau has chosen to emphasize other aspects of the Liberal deficit promise.

"We also promised to lower our net debt-to-GDP during the course of our mandate," Morneau told reporters on Monday. "We intend on keeping that commitment."

Think that might be difficult to accomplish in the given circumstances? Not necessarily.

Ratios are relative

In Stephen Harper government's first fiscal year in power, Canada's debt-to-GDP ratio was at 31.3. A financial crisis and two recessions later — about $150-billion has been added to Canada's debt, but economists estimate as a percentage of the whole economy, it stands at 31.1. It went down.

Even taking into account revised lower GDP forecasts, Morneau could table a budget with $15-billion deficit and still lower the debt-to-GDP ratio.

The budget is months away, so there is is still time for yet more revisions, and  perhaps  some tough choices will be made.

In the meantime, the Liberals are pointing out that the $1.4-billion gap between what the tax cut costs and what the tax hike brings in represents $1.4-billion more in taxpayers pockets — which in turn, they say, ought to stimulate the sagging economy.

Nonetheless, there is the issue of perception.

What is going to be easier for the public to get its head around? That the Liberals have managed to lower the federal debt-to-GDP ratio? Or that they promised deficits under $10-billion, and posted something higher?

On the other hand, the Liberals also promised a new era of openness and transparency.

The reason we know their $10-billion deficit promise seems to be going the way of their 25,000 Syrian refugees by year-end promise? They are telling us every step of the way, as the numbers change.