Depending on the capacity of the scale and the weight of your ingestion device and your container of spice, there are a couple tricks:

Put the ingestion device (maybe a glass dish in the case of nectar collector) on the scale and tare it.  Make sure the ingestion device does not exceed the capacity of your scale.  Then add material directly to the ingestion device and the scale will display the amount of material added.

Put your supply on the scale (in its container, of course) and tare it. As always, make sure you aren't exceeding the total capacity of the scale.  Remove material from your supply and the scale will go into negatives, reflecting how much material you've removed.