> Exodus 36:3-4:
> וַיִּקְח֞וּ מִלִּפְנֵ֣י מֹשֶׁ֗ה אֵ֤ת כָּל־הַתְּרוּמָה֙ אֲשֶׁ֨ר
> הֵבִ֜יאוּ בְּנֵ֣י יִשְׂרָאֵ֗ל לִמְלֶ֛אכֶת עֲבֹדַ֥ת הַקֹּ֖דֶשׁ
> לַעֲשֹׂ֣ת אֹתָ֑הּ וְ֠הֵם הֵבִ֨יאוּ אֵלָ֥יו ע֛וֹד נְדָבָ֖ה בַּבֹּ֥קֶר
> בַּבֹּֽקֶר׃ 
> And they received of Moses all the offering, which the children of
> Israel had brought for the work of the service of the sanctuary,
> wherewith to make it. And they brought yet unto him freewill-offerings
> every morning. 
> Exodus 36:5:
> וַיֹּאמְרוּ֙ אֶל־מֹשֶׁ֣ה לֵּאמֹ֔ר מַרְבִּ֥ים הָעָ֖ם לְהָבִ֑יא מִדֵּ֤י
> הָֽעֲבֹדָה֙ לַמְּלָאכָ֔ה אֲשֶׁר־צִוָּ֥ה יְהוָ֖ה לַעֲשֹׂ֥ת אֹתָֽהּ׃
> And they spoke unto Moses, saying: ‘The people bring much more than
> enough for the service of the work, which the LORD commanded to make.’

The Torah specified exact measurements for nearly every part of the Mishkan and all the tools - the amount of gold & silver and the dimensions of the altar, etc. I assume that there was a head person (or a few people) in charge of inventory. If each day, people were bringing more items, didn't someone tell the people who brought something, "listen, please tell your *shevet* (or whomever) that we are almost at the limit of item X. Don't bring us so much because we will have too much" ?