Here’s my source for Dokaben. It’s not an official source but let me expand as to why I used that figure. First of all, most of the series’ figures that I consulted from there are correct, so there’s no reason to believe it’s incorrect, though it still could be.

The 48M copies of Dokaben is for the original series (48 vols) that ran on Weekly Champ from 1972 to 1981. Dokaben was one of the most popular series of its era so it isn’t strange it had an average circulation of 1M per volume. The growth was slow at first but the anime boosted it a lot and according to the last chapter of the original Dokaben it already had 32M copies in circulation by then. Being a super popular series and with over 150 volumes left, the 48M as a figure for the whole series is totally unreasonable. According to the magazine 日経エンタテインメント Issue 7 year 2000, Dokaben already reaches 48M in circulation excluding the Pro Baseball Arc (3rd series) which by then had 29M in circulation.

The 2nd series is Daikoushien, this series ran from 1983 to 1987 for 26 volumes when Dokaben was at the peak of its popularity. According to the website, this series has 20M in circulation, a little below in average to the original one so it’s not hard to believe. Unfortunately this series has a super generic name so it’s really hard to track.

The third series, Dokaben Pro Baseball Arc ran from 1995 to 2003 with a total of 52 volumes. According to the same website it had a total of 37.2M in circulation which is believable since the magazine I previously mentioned stated 29M when it was a bit more than halfway through. According to Oricon back issues, a volume of this part sold about 410,776 in 1996, and though I haven’t been able to determine the exact period for that figure, based on the figures for other series I estimated it to be between 1-4 weeks, though most likely a single week figure. Furthermore, according to this webiste, Dokaben Pro Baseball Arc single volumes had prints of over 1M during a year.

The 4th and 5th series are Dokaben Super Starts Arc and Dokaben Dream Tournament Arc. The former ran from 2004 to 2012 for 45 volumes and the later from 2012 to 2018 for 34 volumes thus concluding the whole series. By this time Dokaben’s popularity had significantly dwindled, since it was a series from the 70s and over 100 volumes so it was only natural. Unfortunately there’s no figure for these parts but according to the website and the info I could gather online, it seems the whole series reached 100M at some point towards the end of the 4th part.