90m to 227m and bikehike.co.uk puts the distance between the crossroads and the 227m spot height at 1.44km.
According to bikehike.co.uk there's also 20m of descent during the climb, putting the total climb at 137m + 20m = 157m.
157m in 1.44km is > 10%
Also, if you only consider the climb until the final false summit (290m from the spot height point) then it's 123m of climb (89m to 212m) in 1.15km, so the bulk of it is over 10%. This doesn't even include the extra 16m of extra climbing to make up for the small descents putting it at 139m of climbing in 1.15km which makes it almost bang on 1 in 8.