Analysts are taking swings left and right to guess just how many Apple Watches were sold in the June quarter. And the latest comes from market research company Canalys, who estimates 4.2 million units shipped in Apple’s fiscal 2015 third quarter.

This would place the Apple Watch ahead of the Fitbit, Xiaomi and a slew of other smartwatch vendors, according to Canalys. But it also falls within the wide range of analyst estimates that peg sales between 2.85 and 5.7 million units, according to a poll conducted by Fortune.

Even with those educated guesses in the open, nobody knows for sure just how many Apple Watches were sold. Apple Inc. has remained silent on exactly how well the watch has done since its April launch.

That’s not expected to change anytime soon as Apple has bundled the Apple Watch into an “other products” category within its financial reports. That category also includes revenue from Beats Electronics, iPod, Apple TV and accessories. While this keeps specific watch sales out of the public eye, it won’t hide the addition of a couple billion in revenue to the category.

Canalys cited two factors hindering Apple Watch sales: missing the 2014 December quarter and supply constraints in the first couple of months after launch. Its findings are similar to those given by Piper Jaffray senior research analyst, Gene Munster, who estimated Apple Watch sales at around 3 million units.

He pointed to the Apple Watch’s slow rollout and lack of initial in-store sales as headwinds for it. But he expects the watch to hit its breakout stride in a couple years, with sales reaching 14 million in 2016 and 40 million in 2017.

Apple will report its fiscal 2015 third-quarter earnings after the bell on Tuesday, followed by an investor call to discuss the results starting at 5 p.m. EDT/2 p.m. PDT.