If theres a few units, you can overlap those symbols to get more space (maybe even two interleaved rows so new tanks go like /\/\/\ which might take less space). If the rows get too long, cluster them to simplify counting. Like replace every sequence of 5 tanks, with a single symbol that stands for "5 tanks" and is more compact and readable. Mostly overlapping the similar symbols allows making them bigger so it can look like a simplified tank etc.
If theres many units, the player probably doesnt need to see exact numbers, only the total strength and the ratio of unit types. You can represent the ratio of unit types in a constant amount of space (using some bars or symbols sized according to representation or a pie chart...). Then put a single number for the total number of units. This might not work if some units are vastly more numberous than others (like 10000 infantry vs 1 boat), so might want to group the numerous units into bigger ones until the numbers are of similar magnitude. Of course you can add the detailed data in some menu.
If the numbers are big, and the player needs to do a lot of calculation/comparison, I would say its necessary to have the exact numbers there. And add some visual approximation so a force of 1 unit and 100 units are differentiated by more than just two additional digits (different icon/size for example).
You could also represent different unit types and counts using different approaches (like switching to numbers once there start to be too many, if your game changes in nature toward end-game like that). If some unit is never going to be more than 1 or 2, you can change the map icon itself (the blue thing), like add some circles around it. If some unit is always going to be numerous (like if theres always lots of supporting infrantry), just always use a number and find some special spot on the map icon to display it (so there would be a "base strength" like you have the number at the bottom, and "supporting units" individually counted like you have the tiny symbols). Making units special like this might differentiate the units more, so they dont feel all the same with just a different shape and stats (gives impression of higher complexity, and also makes it easier for you as the designer to add that complexity when theres no pressure to keep all units following the same rules).
