Note the future tense. He is saying the enemy is going to bring their main force to Yorktown. He is of course right there.
Johnston eventually has 87 infantry regiments, 4 battalions, 63 artillery batteries, 4 cavalry regiments and some militia. About 100,000 grand aggregate.
About 12,000 grand aggregate were the other side of the James.
Per McClellan, Johnston arrived (past tense) with "heavy reinforcements" yesterday. He does not mention "and more reinforcements are arriving all the time" to suggest that even more troops will be coming to swell that into 100,000+.
But granting that he means "when everyone is up for Johnston" for discussion's sake:
If McClellan is talking "Grand aggregate" for Johnston, what the muffin is up with him listing his own forces as those "for duty" (not clear from his writing whether he means "present for duty equipped" or "present for duty")?
More on that below.
By what measure?
Since he states the enemy is estimated at 200 regiments plus odds and sods it's immediately clear this is an estimate of "grand aggregate". The reasons why grand aggregate was adopted seem to be partially that it was the category Lincoln always used when estimating McClellan's strength.
When his forces are reported by him as "for duty" when talking about how if only he had more men, its not immediately clear that he's using a different set of figures entirely to talk about Rebel numbers.
And I'm honestly not sure which is worse: An apples to oranges comparison to make the odds against him seem worse than he thought they were in the field (as he knows from managing his own army, "total present" and "available for duty" are not identical numbers) or an apples to apples comparison that overstates the number of Confederates against him by a considerable margin but which is attempting to show the odds in the field rather than an intentional misrepresentation of them.
This is the sort of thing that Stanton being an angel would not make any different or any less appalling. Stanton is not responsible for what McClellan did with the forces he had, Stanton is not responsible for McClellan seeing obstacles but not solutions.
Yet Grant seeing more than double at Fort Donelson and again at Shiloh is?
Pinkerton's overestimates are lower than those of Sherman in Kentucky, Grant throughout the whole of 1862, and Meade at Gettysburg.
Not enough to deter Grant from actually pitching into the enemy?
Not enough to make Grant demand other theaters be stripped so that forces can concentrate on his army (as McClellan did after the Seven Days)?
Pinkerton talks about 200,000+ Rebels a year earlier. I don't know Lee's actual aggregate present in either case (the Seven Days or at Gettysburg), but that's much further from his actual fighting force than an estimate of 90,000 infantry, 4-5,000 artillery and 10,000 cavalry is (for Gettysburg). Though as of May 31: ~80,000+Davis + four of Pettigrew's regiments + the 1st MD battalion/2nd MD would add up close to 90,000 (per
http://ebooks.library.cornell.edu/c...o=waro0026;didno=waro0026;view=image;seq=1102 it would be 2,971 aggregate present for Davis and probably over 3,000 for Pettigrew, though in lieu of any good count of the 44th North Carolina I'm hesitant at being too precise there.).
McClellan saw odds and trembled, Meade and Grant did not. There is why they are known as successful generals, and McClellan is known as the arrogant whiner who saw double.
Being a Democrat and an unfriend of Stanton would be minor if not irrelevant had McClellan been the sort of general cut out to lead 100,000 men instead of the sort of general to expect everyone to drop everything for him.
I'm not saying McClellan got all the support possible, but what he did with what's available does not favor compromising