And even those numbers are suspect. They probably represent every soldier on the muster rolls, including those who are in hospital, AWOL, or on detached duty. The number 'present and fit for duty' would be considerably less.
As an example, at the beginning of 1779 the Jamaica garrison was two and a half battalions totalling roughly 1800 men, of whom some 1200 - 1300 were present and fit for duty. During the year five more battalions were sent, bringing the total to over 4,100, yet at the end of the year there were only 3,000 left, half of whom were on the sick list.
(Numbers taken from The War for America, pp 317 - 337.)