"Fuair sé cúig shíniú déag."

Translation: He got fifteen signatures.

[macliam2]

Cúig shíniú dhéag. Déag is lenited as noun ends in vowel and is regular.

[scilling]

The noun wouldn’t have to be regular, e.g. cúig lá dhéag.

[macliam2]

Lá is regular when it comes to counting. Irregulars are: bliain, seachtain, uair, ceann,
cloigeann, orlach, pingin, troigh, slat, trian, ubh - and or course your namesake scilling :)

Samplaí ná dhá bhliain, trí bliana (déag); ceithre horlaí (déag); cúig seachtaine (déag); sé troithe, seacht dtroithe (déag); ocht slata, naoi slata (déag).

Regular examples: dhá lá dhéag, trí mhí dhéag; seacht n-earra dhéag; naoi n-artaire dhéag srl

[scilling]

Thanks for clarifying the meaning of “regular” here.

[larryone]

It got 15 signatures...