Example of too little Thermal Paste

If you apply too little Thermal Paste it may not spread enough to cover the CPU cores.

Here is an example of applying too little Thermal Paste.

The coverage area falls a bit short. It does not quite reach the edge.

However, this will still do the job.

Note: It is better to apply a little less than the ideal amount of Thermal Paste, rather than applying too much which may cause it to spill over the sides.

It is always safer to err on the lesser side.