Hi Jack, if the symbol you are referring to looks like: "a circle with dot in the middle and a water droplet at the 2 o'clock position" this is the reminder to perform a drum cleaning procedure. You can clear this by turning the control knob to the 4 position and then pressing the "Ready In" button.
Better still, just run the drum clean program, no clothes in drum, set to 60 degrees and half a measure of detergent..
As you didn't provide the exact model number, I've taken a guess at which features your version has got, so above info may not apply to some variants. Below you will find a PDF link to the manual for one of the early versions, bring up page 37 and then 32 for details.
https://media3.bosch-home.com/Documents/9001123077_A.pdf
Rupert, December 2019
