I don't know of any precise technical way ,apart from tap tempo on something like KO ;or a sampler like KP3 were you measure it with trimming until a repeat disappears.
But I would recommend train that ear. Use the DJ trick..
Imagine you are drumming over your MS20 groove, with a snare hitting every other beat . Then tune you delay repeat to it buy detecting if the hit (imaginary snare/delay repeat) is early or late. If the repeat is every single beat then tune into that timing. It's just a case of concentrating on the two sounds at once , like a harder version of patting your head and rubbing your tummy-at the same time.
Hope this helps.
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