Probably that set of jumpers set the transformer secondary output voltage.
There's probably two secondary windings in the transformer.
For 220, they're wired in series.
For 110, they're wired parallel.
With it in hand and a ohm meter, I could figure it out.
But from here, that's all I can say.
Proceed cautiously.
Perhaps identify the transformer and find the data sheet. Configuration data should be there
Those boards are probably somewhat generic and have commonality with other products. Perhaps other similar products have documentation.