Hi, there is no concrete rule. You could either decide that you want the default as maxspeed and since the sign is conditional to have conditional:maxspeed. Or you could put maxspeed as 70 and add a conditional for 90 - at least this won't suggest to break the law for consumers which don't support conditionals.

If it was a condition which is applied rarely, I'd definitely put it in conditional:maxspeed.

You should at least add the default speed (90?) as maxspeed if you leave the conditional as 70.

I also suggest removing ;Sa off;Su off - I think these are not required.

Some context if someone stumbles upon these comments:

https://www.mapillary.com/app/?lat=58.18305939999698&lng=25.50511080000001&z=18.531688264196713&pKey=293992547065552&focus=photo&x=0.5808639655721334&y=0.47141229429312625&zoom=2.0930232558139537