Yes, it should be transport capacity (TC).
To find out about it, you might want to read the corresponding article in the
HoI2 Wiki, as well as the
corresponding FAQ page on the same website.
One of the two numbers is the TC you currently have available, the other is the one you are actually using. If you use more TC than you have available, your overall supply efficiency, troop organization regain and movement speed will be reduced, so it is a good idea to avoid using up your TC completely. Two ways people quickly overextend their TC with is by having a large number of undeployed units (e.g. finished production, but not deployed yet), or by using strategic redeployment of units without consideration for the TC they will take up in the process.