O +
significa que o número foi muito longo para caber aqui. Você pode ver diferentes representações do número com o comando E
.
Na página principal (1) :
E : Extend-Memory-Scale in Summary Area
With this command you can cycle through the available summary area memory scaling which ranges from KiB (kibibytes or 1,024 bytes) through EiB (exbibytes or 1,152,921,504,606,846,976 bytes).
If you see a '+' between a displayed number and the following label, it means that top was forced to truncate some portion of that number. By raising the scaling factor, such truncation can be avoided.