Sales vs Target Measure (with example PBI)

Hi guys, 

I want to calculate a Sales / Target ratio per month only for supplier A. 

I have a table with sales and target per supplier. The sales are per month. The targets are for the whole period. 

The goal should be to divide each monthly row by 5.000. The sales are only for supplier A therefore only the 5.000 shall be used:

The example PBI file is here: https://easyupload.io/r4g589

Anybody an idea how to write the Sales Target ratio measure?

Thanks!