When I query your nameserver, I get the same result, so I think this is working correctly:
$ dig aluekouluttaja.fi. NSEC @213.250.93.67
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7670
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1680
;; QUESTION SECTION:
;; ANSWER SECTION:
;; Query time: 118 msec
;; SERVER: 213.250.93.67#53(213.250.93.67)
;; WHEN: Tue Oct 01 10:14:49 EDT 2019
;; MSG SIZE rcvd: 109