Constant capital and variable capital in Volume 1 do not refer to hypothetical quantities of money capital, which are assumed to be equal to the values of the means of production and means of subsistence (as in the standard interpretation). Instead, constant capital and variable capital in Volume 1 refer to actual quantities of money capital, which tend to be equal to the prices of production of the means of production and means of subsistence, although prices of production cannot be explained in Volume 1, because prices of production have to do with the distribution of surplus-value; and before the distribution of surplus-value can be explained, the total amount of surplus-value to be distributed must first be determined--this being the main task of Volume 1.
Fred Moseley. Money and Totality. Brill: Leiden, 2015. Ch. 1, pgs. 7-8