Here you set a fixed-asset sales invoice for myDATA.
When you sell a fixed asset and need the correct fixed-asset classification.
Open Settings → Tax connections → Variable mapping and fill the yellow myDATA fields on the related document / VAT. The basics are in the main myDATA mapping article.
On-screen steps
What the codes mean
Usually income classification category1_4 (income from sale of fixed assets) with E3 series E3_880_* (fixed-asset sales wholesale/retail/foreign).