The indeclinable word yāvat when it signifies limitation, is invariably compounded with a word ending in a case-affix which is in construction with it, and the compound so formed is called avyayībhāva,
The word अवधारण means accurate ascertainment, restriction or limitation. As, यावदमत्रं ब्राह्मणानामन्त्रयस्व invite so many Bráhmanas only and not more as there are pots': i.e., if there are five pots then invite five Bráhmans; if six pots, then invite six Bráhmans.
Why do we say 'when meaning limitation'? Observe यावद्दत्तं तावत् भुक्तम् 'I ate so long as it was given to me,' i.e. I do not know for certainty how much I have eaten.,