There are considerable differences in the way Finnic languages treat numerals from their treatment in, for example, Indo-European languages. For example, in most Finnic languages a noun following a numeral larger than 1 is in singular partitive in the absence of other grammatical relations, in case of grammatical relations both the numeral and the noun take the respective case in singular.
In text corpora, however, there appears to be considerable variability in how numerals are treated, often in a way reminiscent of Indo-European languages, very likely under the influence of Latvian.
Considerable variations can be encountered in the treatment of numerals, for example, only the noun expressing specific relationships without modifying the numeral: seis skūolsõ (seven:sg.nom. school:sg.ines.) (not seisõs skūolsõ, cf., standard Estonian seitsmes koolis), kuolm āigastõks (three:sg.nom. year:sg.instr.) (not kuolmõks āigastõks, cf., Estonian kolmeks aastaks) and vice versa, e.g., kuolms ežmižis lugdõbrōntiš (peculiarly the nouns in the last example are in plural as well.) (Source)
Likely under Latvian influence where some numerals are indeclinable and in all cases take nouns in plural. Following numeral usage conventions of other Finnic languages could arguably be the most consistent approach.