Reports on Thursday suggested that the pay-day loans company had made the "significant" gesture after discussions with BDO, the accountancy firm now running the Tynecastle club, but Press Association Sport understands that the cash injection is substantially less than the quoted figure.
A source close to the club confirmed the amount was a "significant five-figure sum", with a number of instalments, which had been due to be paid before the company's three-year backing ends next summer, brought forward.
Jambos officials - who still need to raise £750,000 to keep the club afloat until the start of the new season - feared that news of the cash advance would see season-ticket sales ease off with them less than halfway towards the 3,000 target they still need to sell.
Manager Gary Locke said: "It's great that one of our main sponsors has shown they are willing to back the football club. But contrary to reports, it is nowhere near the figure that has been suggested. I have to reiterate to our supporters get down and buy your season tickets because we do still have a long way to go.
"The support we have had from the fans has been nothing short of incredible but we need to get the message out there that (the Wonga money) is not the figure people have been suggesting. It's a great help to us, don't get me wrong, but we do need as much money coming into us as we can."
Meanwhile, Locke has told the Rangers fans who say they would have snubbed a proposed friendly with the administration-hit Jambos that they do not need their help. Reports this week claimed the Tynecastle manager had approached Ibrox counterpart Ally McCoist in the hope of lining up a fundraising match to help the financially stricken capital club.
But a spokesman for the Rangers Supporters Association claimed the Light Blues faithful would not have attended the fixture after Hearts voted against plans to allow Rangers to re-enter the Scottish Premier League following their liquidation last summer.
Locke, though, insists he spoke to McCoist before Hearts called in administrators BDO and claims the only backing they need is from the Gorgie support, and he said: "I was asked a question about whether I'd spoken to Ally. Of course I did but it was really just to see what his pre-season plans were, just because we needed a game.
"It was done before we went into administration and was the same as I've done with just about every manager in Britain. Ally said that Rangers had their pre-season plans in place. That was as far as it went. Then I picked up papers saying I was begging for a game. That's certainly not the case."