The volume you can inject, with a reasonable precision and reproducibility depends of what injection mode you are using. If you are using Partial Loop mode (with Pressure assist) the specifications says:
10-50% of loop volume = 1-5ul for a 10ul loop. If you are using Partial Loop Using Needle Overfill (PLUNO) (which is what I would recommend for a 10ul loop volume) the specs are 10-75% of loop volume : 1-7,5ul.
Please be aware of the fact the when using PLUNO the sample manager will draw and extra 15ul of sample on top of the volume you specify.
I hope this answers your question.