Dragon Rampant rules: clarification on Summoners

[coopuk]

I'm reading through Dragon Rampant rules and the Summoner don't make sense to me:

If you deploy a Summoner in a scenario where some of your units are deployed off-table, a -1 modifier is applied to all Summoning activation tests for the scenario's duration


My understanding is that for the Summoners to have something to summon, you need to have units deployed off-table. So it wouldn't make sense to deploy Summoner at a higher cost without units deployed off-table.

The confusion is why is this -1 modifier not added to the activation score, and needs to be individually listed? It makes me feel that I'm missing something in the rules.

Thoughts/comments please!

[Pattus Magnus]

If the -1 is applied to the target number, it would be an advantage. I’m not sure whether that is the intention behind that rule, though. Hopefully someone very familiar with the rules will weigh in.